Nullable refernce types refactoring

WotBlitzStatisticsPro.Common/Dictionaries/AchievementOption.cs

@@ -10,22 +10,22 @@ namespace WotBlitzStatisticsPro.Common.Dictionaries
 		///<summary>
         /// Achievement option description
         ///</summary>
-        public List<LocalizableString> Description { get; set; }
+        public List<LocalizableString>? Description { get; set; }
 
         ///<summary>
         /// Image link
         ///</summary>
-        public string Image { get; set; }
+        public string? Image { get; set; }
 
         ///<summary>
         /// Image 180x180px link
         ///</summary>
-        public string ImageBig { get; set; }
+        public string? ImageBig { get; set; }
 
         /// <summary>
         /// Achievement option name
         /// </summary>
-        public List<LocalizableString> Name { get; set; }
+        public List<LocalizableString>? Name { get; set; }
 
 	}
 }

WotBlitzStatisticsPro.Common/Dictionaries/IVehiclesDictionary.cs

@@ -75,22 +75,22 @@ namespace WotBlitzStatisticsPro.Common.Dictionaries
         ///<summary>
         /// Engines id list
         ///</summary>
-        int[] Engines { get; set; }
+        int[]? Engines { get; set; }
 
 		///<summary>
 		/// Guns id list
 		///</summary>
-		int[] Guns { get; set; }
+		int[]? Guns { get; set; }
 
 		///<summary>
 		/// List of compatible suspensions
 		///</summary>
-		int[] Suspensions { get; set; }
+		int[]? Suspensions { get; set; }
 
 		///<summary>
 		/// List of compatible turrets ids
 		///</summary>
-		int[] Turrets { get; set; }
+		int[]? Turrets { get; set; }
 
 	}
 }

WotBlitzStatisticsPro.Common/Dictionaries/LocalizableString.cs

@@ -15,6 +15,6 @@ namespace WotBlitzStatisticsPro.Common.Dictionaries
         /// <summary>
         /// Localizable string.
         /// </summary>
-        public string Value { get; set; }
+        public string? Value { get; set; }
     }
 }

WotBlitzStatisticsPro.Common/Model/AccountInfoHistoryResponse.cs

@@ -20,26 +20,26 @@ namespace WotBlitzStatisticsPro.Common.Model
         ///<summary>
         /// Player's nick
         ///</summary>
-        public string Nickname { get; set; }
+        public string? Nickname { get; set; }
 
         /// <summary>
         /// Overall statistics since account creation
         /// </summary>
-        public ShortStatistics OverallAccountStatistics { get; set; }
+        public ShortStatistics? OverallAccountStatistics { get; set; }
 
         /// <summary>
         /// Statistics for period
         /// </summary>
-        public ShortStatistics PeriodAccountStatistics { get; set; }
+        public ShortStatistics? PeriodAccountStatistics { get; set; }
 
         /// <summary>
         /// Difference between start and end of the period
         /// </summary>
-        public StatisticsDifference PeriodDifference { get; set; }
+        public StatisticsDifference? PeriodDifference { get; set; }
 
         /// <summary>
         /// The detailed history
         /// </summary>
-        public StatisticsDifference[] StatisticsHistory { get; set; }
+        public StatisticsDifference[]? StatisticsHistory { get; set; }
     }
 }

WotBlitzStatisticsPro.Common/Model/AccountInfoResponse.cs

@@ -26,7 +26,7 @@ namespace WotBlitzStatisticsPro.Common.Model
         ///<summary>
         /// Player's nick
         ///</summary>
-        public string Nickname { get; set; }
+        public string? Nickname { get; set; }
 
 		///<summary>
 		/// Battles count
@@ -151,7 +151,7 @@ namespace WotBlitzStatisticsPro.Common.Model
         /// <summary>
         /// All player's tanks
         /// </summary>
-        public List<TankInfoResponse> Tanks { get; set; }
+        public List<TankInfoResponse>? Tanks { get; set; }
 
 	}
 }

WotBlitzStatisticsPro.Common/Model/AccountsSearchResponse.cs

@@ -14,6 +14,6 @@ namespace WotBlitzStatisticsPro.Common.Model
         /// <summary>
         /// Found accounts list
         /// </summary>
-        public ICollection<AccountsSearchResponseItem> Accounts { get; set; }
+        public ICollection<AccountsSearchResponseItem>? Accounts { get; set; }
     }
 }

WotBlitzStatisticsPro.Common/Model/AccountsSearchResponseItem.cs

@@ -13,6 +13,6 @@
         ///<summary>
         /// Player nick
         ///</summary>
-        public string Nickname { get; set; }
+        public string? Nickname { get; set; }
     }
 }

WotBlitzStatisticsPro.Common/Model/ClanSearchResponse.cs

@@ -14,6 +14,6 @@ namespace WotBlitzStatisticsPro.Common.Model
         /// <summary>
         /// List of clans
         /// </summary>
-        public ICollection<ClanSearchResponseItem> Clans { get; set; }
+        public ICollection<ClanSearchResponseItem>? Clans { get; set; }
     }
 }

WotBlitzStatisticsPro.Common/Model/ClanSearchResponseItem.cs

@@ -13,12 +13,12 @@
         ///<summary>
         /// Clan Tag
         ///</summary>
-        public string Tag { get; set; }
+        public string? Tag { get; set; }
 
         ///<summary>
         /// Clan Name
         ///</summary>
-        public string Name { get; set; }
+        public string? Name { get; set; }
 
         ///<summary>
         /// Clan created at. (UNIX Epoch time)

WotBlitzStatisticsPro.Common/Model/StatisticsDifference.cs

@@ -15,32 +15,32 @@ namespace WotBlitzStatisticsPro.Common.Model
         ///<summary>
         /// Difference in Battles count
         ///</summary>
-        public StatisticsDifferenceItem<long> Battles { get; set; }
+        public StatisticsDifferenceItem<long>? Battles { get; set; }
 
         /// <summary>
         /// Difference in Average tier
         /// </summary>
-        public StatisticsDifferenceItem<double> AvgTier { get; set; }
+        public StatisticsDifferenceItem<double>? AvgTier { get; set; }
 
         /// <summary>
         /// Difference in Wn7 coefficient
         /// </summary>
-        public StatisticsDifferenceItem<double> Wn7 { get; set; }
+        public StatisticsDifferenceItem<double>? Wn7 { get; set; }
 
         /// <summary>
         /// Difference in Player's win rate
         /// </summary>
-        public StatisticsDifferenceItem<decimal> WinRate { get; set; }
+        public StatisticsDifferenceItem<decimal>? WinRate { get; set; }
 
         /// <summary>
         /// Difference in Player's average damage
         /// </summary>
-        public StatisticsDifferenceItem<decimal> AvgDamage { get; set; }
+        public StatisticsDifferenceItem<decimal>? AvgDamage { get; set; }
 
         /// <summary>
         /// Difference in Player's average XP
         /// </summary>
-        public StatisticsDifferenceItem<decimal> AvgXp { get; set; }
+        public StatisticsDifferenceItem<decimal>? AvgXp { get; set; }
 
     }
 }

WotBlitzStatisticsPro.Common/Model/TankInfoResponse.cs

@@ -150,17 +150,17 @@ namespace WotBlitzStatisticsPro.Common.Model
         /// <summary>
         /// Tank name
         /// </summary>
-        public string Name { get; set; }
+        public string? Name { get; set; }
 
         /// <summary>
         /// Tank nation dictionary identifier
         /// </summary>
-        public string TankNationId { get; set; }
+        public string? TankNationId { get; set; }
 
         /// <summary>
         /// Localized tank nation name
         /// </summary>
-        public string TankNation { get; set; }
+        public string? TankNation { get; set; }
 
         /// <summary>
         /// Tank tier
@@ -170,12 +170,12 @@ namespace WotBlitzStatisticsPro.Common.Model
         /// <summary>
         /// Tank type dictionary identifier
         /// </summary>
-        public string TankTypeId { get; set; }
+        public string? TankTypeId { get; set; }
 
         /// <summary>
         /// Localized tank type name
         /// </summary>
-        public string TankType { get; set; }
+        public string? TankType { get; set; }
 
         /// <summary>
         /// Is it premium tank or not

WotBlitzStatisticsPro.Common/Model/UpdateDictionariesResponseItem.cs

@@ -13,6 +13,6 @@
         /// <summary>
         /// A bit summary about what have been updated
         /// </summary>
-        public string Description { get; set; }
+        public string? Description { get; set; }
     }
 }

WotBlitzStatisticsPro.Common/WotBlitzStatisticsPro.Common.csproj

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <TargetFramework>net5.0</TargetFramework>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
 </Project>

WotBlitzStatisticsPro.DataAccess/Model/Accounts/AccountInfo.cs

@@ -1,4 +1,7 @@
-using MongoDB.Bson.Serialization.Attributes;
+using System;
+using System.ComponentModel.DataAnnotations;
+using System.Diagnostics.CodeAnalysis;
+using MongoDB.Bson.Serialization.Attributes;
 using WotBlitzStatisticsPro.Common.Model;
 
 namespace WotBlitzStatisticsPro.DataAccess.Model.Accounts
@@ -32,7 +35,8 @@ namespace WotBlitzStatisticsPro.DataAccess.Model.Accounts
         ///<summary>
         /// Player's nick
         ///</summary>
-        public string Nickname { get; set; }
+        [Required]
+        public string Nickname { get; set; } = string.Empty;
 
         ///<summary>
         /// Player information update date

WotBlitzStatisticsPro.DataAccess/Model/Accounts/AccountInfoHistoryKey.cs

@@ -19,14 +19,14 @@ namespace WotBlitzStatisticsPro.DataAccess.Model.Accounts
 
         public int LastBattleTime { get; set; }
 
-        public bool Equals(AccountInfoHistoryKey other)
+        public bool Equals(AccountInfoHistoryKey? other)
         {
             if (ReferenceEquals(null, other)) return false;
             if (ReferenceEquals(this, other)) return true;
             return AccountId == other.AccountId && LastBattleTime == other.LastBattleTime;
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (ReferenceEquals(null, obj)) return false;
             if (ReferenceEquals(this, obj)) return true;

WotBlitzStatisticsPro.DataAccess/Model/Accounts/TankInfo.cs

@@ -7,7 +7,7 @@ namespace WotBlitzStatisticsPro.DataAccess.Model.Accounts
     {
         public TankInfo()
         {
-            
+            TankInfoId = new TankInfoKey();
         }
 
         public TankInfo(long accountId, long tankId)

WotBlitzStatisticsPro.DataAccess/Model/Accounts/TankInfoHistory.cs

@@ -7,7 +7,7 @@ namespace WotBlitzStatisticsPro.DataAccess.Model.Accounts
 
         public TankInfoHistory()
         {
-            
+            TankInfoHistoryId = new TankInfoHistoryKey();
         }
 
         public TankInfoHistory(long accountId, long tankId, int lastBattleTime)

WotBlitzStatisticsPro.DataAccess/Model/Accounts/TankInfoHistoryKey.cs

@@ -31,14 +31,14 @@ namespace WotBlitzStatisticsPro.DataAccess.Model.Accounts
         ///</summary>
         public int LastBattleTime { get; set; }
 
-        public bool Equals(TankInfoHistoryKey other)
+        public bool Equals(TankInfoHistoryKey? other)
         {
             if (ReferenceEquals(null, other)) return false;
             if (ReferenceEquals(this, other)) return true;
             return AccountId == other.AccountId && TankId == other.TankId && LastBattleTime == other.LastBattleTime;
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (ReferenceEquals(null, obj)) return false;
             if (ReferenceEquals(this, obj)) return true;

WotBlitzStatisticsPro.DataAccess/Model/Accounts/TankInfoKey.cs

@@ -25,14 +25,14 @@ namespace WotBlitzStatisticsPro.DataAccess.Model.Accounts
         ///</summary>
         public long TankId { get; set; }
 
-        public bool Equals(TankInfoKey other)
+        public bool Equals(TankInfoKey? other)
         {
             if (ReferenceEquals(null, other)) return false;
             if (ReferenceEquals(this, other)) return true;
             return AccountId == other.AccountId && TankId == other.TankId;
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             if (ReferenceEquals(null, obj)) return false;
             if (ReferenceEquals(this, obj)) return true;

WotBlitzStatisticsPro.DataAccess/Model/AchievementDictionary.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using MongoDB.Bson.Serialization.Attributes;
 using WotBlitzStatisticsPro.Common.Dictionaries;
 
@@ -6,19 +7,18 @@ namespace WotBlitzStatisticsPro.DataAccess.Model
 {
     public class AchievementDictionary : IAchievementDictionary
     {
-        [BsonId]
-        public string AchievementId { get; set; }
-        public List<LocalizableString> Condition { get; set; }
-        public List<LocalizableString> Description { get; set; }
-        public List<LocalizableString> HeroInfo { get; set; }
-        public string Image { get; set; }
-        public string ImageBig { get; set; }
-        public List<LocalizableString> Name { get; set; }
+        [BsonId] public string AchievementId { get; set; } = string.Empty;
+        public List<LocalizableString> Condition { get; set; } = Enumerable.Empty<LocalizableString>().ToList();
+        public List<LocalizableString> Description { get; set; } = Enumerable.Empty<LocalizableString>().ToList();
+        public List<LocalizableString> HeroInfo { get; set; } = Enumerable.Empty<LocalizableString>().ToList();
+        public string Image { get; set; } = string.Empty;
+        public string ImageBig { get; set; } = string.Empty;
+        public List<LocalizableString> Name { get; set; } = Enumerable.Empty<LocalizableString>().ToList();
         public long? Order { get; set; }
         public bool Outdated { get; set; }
-        public string SectionId { get; set; }
+        public string SectionId { get; set; } = string.Empty;
         public long? SectionOrder { get; set; }
-        public string Type { get; set; }
-        public List<AchievementOption> Options { get; set; }
+        public string Type { get; set; } = string.Empty;
+        public List<AchievementOption> Options { get; set; } = Enumerable.Empty<AchievementOption>().ToList();
     }
 }

WotBlitzStatisticsPro.DataAccess/Model/AchievementSectionDictionary.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using MongoDB.Bson.Serialization.Attributes;
 using WotBlitzStatisticsPro.Common.Dictionaries;
 
@@ -6,9 +7,10 @@ namespace WotBlitzStatisticsPro.DataAccess.Model
 {
     public class AchievementSectionDictionary: IAchievementSectionDictionary
     {
-        [BsonId]
-        public string AchievementSectionId { get; set; }
+        [BsonId] public string AchievementSectionId { get; set; } = string.Empty;
         public int Order { get; set; }
-        public List<LocalizableString> AchievementSectionNames { get; set; }
+
+        public List<LocalizableString> AchievementSectionNames { get; set; } =
+            Enumerable.Empty<LocalizableString>().ToList();
     }
 }

WotBlitzStatisticsPro.DataAccess/Model/ClanRoleDictionary.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using MongoDB.Bson.Serialization.Attributes;
 using WotBlitzStatisticsPro.Common.Dictionaries;
 
@@ -6,8 +7,8 @@ namespace WotBlitzStatisticsPro.DataAccess.Model
 {
     public class ClanRoleDictionary : IClanRoleDictionary
     {
-        [BsonId]
-        public string ClanRoleId { get; set; }
-        public List<LocalizableString> ClanRoleNames { get; set; }
+        [BsonId] public string ClanRoleId { get; set; } = string.Empty;
+        public List<LocalizableString> ClanRoleNames { get; set; } =
+            Enumerable.Empty<LocalizableString>().ToList();
     }
 }

WotBlitzStatisticsPro.DataAccess/Model/LanguageDictionary.cs

@@ -5,9 +5,8 @@ namespace WotBlitzStatisticsPro.DataAccess.Model
 {
     public class LanguageDictionary: ILanguageDictionary
     {
-        [BsonId]
-        public string LanguageId { get; set; }
+        [BsonId] public string LanguageId { get; set; } = string.Empty;
 
-        public string LanguageName { get; set; }
+        public string LanguageName { get; set; } = string.Empty;
     }
 }

WotBlitzStatisticsPro.DataAccess/Model/NationDictionary.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using MongoDB.Bson.Serialization.Attributes;
 using WotBlitzStatisticsPro.Common.Dictionaries;
 
@@ -6,8 +7,8 @@ namespace WotBlitzStatisticsPro.DataAccess.Model
 {
     public class NationDictionary : INationDictionary
     {
-        [BsonId]
-        public string NationId { get; set; }
-        public List<LocalizableString> NationNames { get; set; }
+        [BsonId] public string NationId { get; set; } = string.Empty;
+        public List<LocalizableString> NationNames { get; set; } =
+            Enumerable.Empty<LocalizableString>().ToList();
     }
 }

WotBlitzStatisticsPro.DataAccess/Model/VehicleTypeDictionary.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using MongoDB.Bson.Serialization.Attributes;
 using WotBlitzStatisticsPro.Common.Dictionaries;
 
@@ -6,8 +7,8 @@ namespace WotBlitzStatisticsPro.DataAccess.Model
 {
     public class VehicleTypeDictionary : IVehicleTypeDictionary
     {
-        [BsonId]
-        public string VehicleTypeId { get; set; }
-        public List<LocalizableString> VehicleTypeNames { get; set; }
+        [BsonId] public string VehicleTypeId { get; set; } = string.Empty;
+
+        public List<LocalizableString> VehicleTypeNames { get; set; } = Enumerable.Empty<LocalizableString>().ToList();
     }
 }

WotBlitzStatisticsPro.DataAccess/Model/VehiclesDictionary.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using MongoDB.Bson.Serialization.Attributes;
 using WotBlitzStatisticsPro.Common.Dictionaries;
 
@@ -8,21 +9,25 @@ namespace WotBlitzStatisticsPro.DataAccess.Model
     {
         [BsonId]
         public long TankId { get; set; }
-        public List<LocalizableString> Name { get; set; }
-        public List<LocalizableString> Description { get; set; }
+        public List<LocalizableString> Name { get; set; } =
+            Enumerable.Empty<LocalizableString>().ToList();
+        public List<LocalizableString> Description { get; set; } =
+            Enumerable.Empty<LocalizableString>().ToList();
         public bool IsPremium { get; set; }
-        public string TypeId { get; set; }
-        public string NationId { get; set; }
+        public string TypeId { get; set; } = string.Empty;
+        public string NationId { get; set; } = string.Empty;
         public int Tier { get; set; }
-        public string PreviewImage { get; set; }
-        public string NormalImage { get; set; }
+        public string PreviewImage { get; set; } = string.Empty;
+        public string NormalImage { get; set; } = string.Empty;
         public decimal PriceCredit { get; set; }
         public decimal PriceGold { get; set; }
-        public List<VehiclePriceInXp> NexTanksInTree { get; set; }
-        public List<VehiclePriceInXp> PriceXp { get; set; }
-        public int[] Engines { get; set; }
-        public int[] Guns { get; set; }
-        public int[] Suspensions { get; set; }
-        public int[] Turrets { get; set; }
+        public List<VehiclePriceInXp> NexTanksInTree { get; set; } =
+            Enumerable.Empty<VehiclePriceInXp>().ToList();
+        public List<VehiclePriceInXp> PriceXp { get; set; } =
+            Enumerable.Empty<VehiclePriceInXp>().ToList();
+        public int[]? Engines { get; set; }
+        public int[]? Guns { get; set; }
+        public int[]? Suspensions { get; set; }
+        public int[]? Turrets { get; set; }
     }
 }

WotBlitzStatisticsPro.DataAccess/WotBlitzStatisticsPro.DataAccess.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net5.0</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

WotBlitzStatisticsPro.GraphQl/MongoSettings.cs

@@ -4,7 +4,7 @@ namespace WotBlitzStatisticsPro.GraphQl
 {
     public class MongoSettings : IMongoSettings
     {
-        public string ConnectionString { get; set; }
-        public string DatabaseName { get; set; }
+        public string ConnectionString { get; set; } = string.Empty;
+        public string DatabaseName { get; set; } = string.Empty;
     }
 }

WotBlitzStatisticsPro.GraphQl/WargamingApiSettings.cs

@@ -4,8 +4,8 @@ namespace WotBlitzStatisticsPro.GraphQl
 {
     /// <inheritdoc />
     public class WargamingApiSettings : IWargamingApiSettings
-	{
+    {
         /// <inheritdoc />
-        public string ApplicationId { get; set; }
-	}
+        public string ApplicationId { get; set; } = string.Empty;
+    }
 }

WotBlitzStatisticsPro.GraphQl/WotBlitzStatisticsPro.GraphQl.csproj

@@ -4,6 +4,7 @@
     <TargetFramework>net5.0</TargetFramework>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <NoWarn>$(NoWarn);1591</NoWarn>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/AccountHistoryInformationPipelineContextData.cs

@@ -13,14 +13,14 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline
 
         public DateTime LastBattleSince { get; }
 
-        public AccountInfo DbAccountInfo { get; set; }
+        public AccountInfo? DbAccountInfo { get; set; }
 
-        public IStatistics[] History { get; set; }
-        public ShortStatistics OverallStatistics { get; set; }
-        public ShortStatistics PeriodAccountStatistics { get; set; }
-        public StatisticsDifference PeriodDifference { get; set; }
-        public StatisticsDifference[] StatisticsHistory { get; set; }
+        public IStatistics[]? History { get; set; }
+        public ShortStatistics? OverallStatistics { get; set; }
+        public ShortStatistics? PeriodAccountStatistics { get; set; }
+        public StatisticsDifference? PeriodDifference { get; set; }
+        public StatisticsDifference[]? StatisticsHistory { get; set; }
 
-        public AccountInfoHistoryResponse Response { get; set; }
+        public AccountInfoHistoryResponse? Response { get; set; }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/AccountInformationPipelineContextData.cs

@@ -6,17 +6,17 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline
 {
     public class AccountInformationPipelineContextData : IDatabasePipelineContextData
     {
-        public AccountInfo AccountInfo { get; set; }
+        public AccountInfo? AccountInfo { get; set; }
 
-        public AccountInfoHistory AccountInfoHistory { get; set; }
+        public AccountInfoHistory? AccountInfoHistory { get; set; }
 
-        public List<TankInfo> Tanks { get; set; }
+        public List<TankInfo>? Tanks { get; set; }
 
-        public Dictionary<long, TankInfoHistory> TanksHistory { get; set; }
+        public Dictionary<long, TankInfoHistory>? TanksHistory { get; set; }
 
-        public AccountInfoResponse Response { get; set; }
+        public AccountInfoResponse? Response { get; set; }
 
-        public AccountInfo DbAccountInfo { get; set; }
+        public AccountInfo? DbAccountInfo { get; set; }
 
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/IDatabasePipelineContextData.cs

@@ -5,6 +5,6 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline
 {
     public interface IDatabasePipelineContextData
     {
-        AccountInfo DbAccountInfo { get; set; }
+        AccountInfo? DbAccountInfo { get; set; }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/IStatisticsPipelineData.cs

@@ -4,15 +4,15 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline
 {
     public interface IStatisticsPipelineData
     {
-        IStatistics[] History { get; set; }
+        IStatistics[]? History { get; set; }
 
-        ShortStatistics OverallStatistics { get; set; }
+        ShortStatistics? OverallStatistics { get; set; }
 
-        public ShortStatistics PeriodAccountStatistics { get; set; }
+        public ShortStatistics? PeriodAccountStatistics { get; set; }
 
-        public StatisticsDifference PeriodDifference { get; set; }
+        public StatisticsDifference? PeriodDifference { get; set; }
 
-        public StatisticsDifference[] StatisticsHistory { get; set; }
+        public StatisticsDifference[]? StatisticsHistory { get; set; }
 
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/OperationContext/OperationContext.cs

@@ -2,7 +2,7 @@
 {
     public class OperationContext : IOperationContext
     {
-        private object _contextData;
+        private object? _contextData;
 
 
         public OperationContext(AccountRequest request)
@@ -21,7 +21,7 @@
         {
             _contextData ??= default(TContextData);
 
-            return (TContextData)_contextData;
+            return (TContextData)_contextData!;
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/BuildAccountInfoResponseOperation.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using AutoMapper;
+using Microsoft.Extensions.Logging;
 using WotBlitzStatisticsPro.Common.Dictionaries;
 using WotBlitzStatisticsPro.Common.Model;
 using WotBlitzStatisticsPro.DataAccess;
@@ -17,17 +18,31 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
     {
         private readonly IMapper _mapper;
         private readonly IDictionariesDataAccessor _dictionariesDataAccessor;
+        private readonly ILogger<BuildAccountInfoResponseOperation> _logger;
 
-        public BuildAccountInfoResponseOperation(IMapper mapper, IDictionariesDataAccessor dictionariesDataAccessor)
+        public BuildAccountInfoResponseOperation(
+            IMapper mapper, 
+            IDictionariesDataAccessor dictionariesDataAccessor,
+            ILogger<BuildAccountInfoResponseOperation> logger)
         {
             _mapper = mapper;
             _dictionariesDataAccessor = dictionariesDataAccessor;
+            _logger = logger;
         }
 
-        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<AccountInformationPipelineContextData>();
 
+            if (contextData?.AccountInfo == null
+                || contextData?.Tanks == null
+                || contextData?.TanksHistory == null)
+            {
+                _logger.LogInformation(
+                    $"contextData or AccountInfo or Tanks or TanksHistory is null");
+                return;
+            }
+
             contextData.Response = _mapper.Map<AccountInfo, AccountInfoResponse>(contextData.AccountInfo);
             contextData.Response = _mapper.Map(contextData.AccountInfoHistory, contextData.Response);
 
@@ -48,13 +63,23 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
                         opt.Items["language"] = context.Request.RequestLanguage;
                         opt.AfterMap((src, dest) =>
                         {
-                            dest.TankType = tankTypes.ContainsKey(dest.TankTypeId) ? tankTypes[dest.TankTypeId] : "-";
-                            dest.TankNation = nations.ContainsKey(dest.TankNationId) ? nations[dest.TankNationId] : "-";
+                            if(dest?.TankTypeId != null)
+                            {
+                                dest.TankType = tankTypes.ContainsKey(dest.TankTypeId)
+                                    ? tankTypes[dest.TankTypeId]
+                                    : "-";
+                            }
+                            if(dest?.TankNationId != null)
+                            {
+                                dest.TankNation = nations.ContainsKey(dest.TankNationId)
+                                    ? nations[dest.TankNationId]
+                                    : "-";
+                            }
                         });
                     });
             });
 
-            await next.Invoke(context);
+            if (next != null) await next.Invoke(context);
         }
 
         private static IVehiclesDictionary CreateStubVehicle()

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/CalculateStatisticsOperation.cs

@@ -17,9 +17,16 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
             _dictionariesDataAccessor = dictionariesDataAccessor;
         }
 
-        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<AccountInformationPipelineContextData>();
+            if (contextData?.AccountInfo == null ||
+                contextData?.AccountInfoHistory == null ||
+                contextData?.Tanks == null ||
+                contextData?.TanksHistory == null)
+            {
+                return;
+            }
 
             var tankIds = contextData.Tanks.Select(t => t.TankId).ToArray();
             var tankTires = await _dictionariesDataAccessor.GetTankTires(tankIds);
@@ -36,7 +43,7 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
             contextData.AccountInfoHistory.CalculateMiddleTier(contextData.TanksHistory.Values.ToList(), tankTires);
             contextData.AccountInfoHistory.CalculateWn7();
 
-            await next.Invoke(context);
+            if (next != null) await next.Invoke(context);
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/CheckIfHistoryIsEmptyOperation.cs

@@ -16,11 +16,11 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
         }
 
 
-        public Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<IStatisticsPipelineData>();
 
-            if (contextData.History == null ||
+            if (contextData?.History == null ||
                 contextData.History.Length == 0)
             {
                 _logger.LogInformation(
@@ -28,7 +28,7 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
                 return Task.CompletedTask;
             }
 
-            return next.Invoke(context);
+            return next != null ? next.Invoke(context) : Task.CompletedTask;
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/CheckLAstBattleDateOperation.cs

@@ -15,16 +15,16 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
             _logger = logger;
         }
 
-        public Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<AccountInformationPipelineContextData>();
 
             if (contextData.DbAccountInfo == null ||
-                contextData.DbAccountInfo.LastBattleTime < contextData.AccountInfo.LastBattleTime)
+                contextData.DbAccountInfo.LastBattleTime < contextData.AccountInfo?.LastBattleTime)
             {
-                return next.Invoke(context);
+                if (next != null) return next.Invoke(context);
             }
-            _logger.LogInformation($"Exiting without saving. Db LastBattleTime: {contextData.DbAccountInfo.LastBattleTime}, WG LastBattleTime: {contextData.AccountInfo.LastBattleTime}");
+            _logger.LogInformation($"Exiting without saving. Db LastBattleTime: {contextData.DbAccountInfo?.LastBattleTime}, WG LastBattleTime: {contextData.AccountInfo?.LastBattleTime}");
             return Task.CompletedTask;
         }
     }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/FillAccountInfoHistoryResponse.cs

@@ -9,10 +9,15 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
 {
     public class FillAccountInfoHistoryResponse : IOperation<IOperationContext>
     {
-        public Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<AccountHistoryInformationPipelineContextData>();
 
+            if (contextData?.DbAccountInfo == null)
+            {
+                return next != null ? next.Invoke(context) : Task.CompletedTask;
+            }
+
             contextData.Response = new AccountInfoHistoryResponse
             {
                 AccountId = context.Request.AccountId,
@@ -24,7 +29,7 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
                 OverallAccountStatistics = contextData.OverallStatistics
             };
 
-            return next.Invoke(context);
+            return next != null ? next.Invoke(context) : Task.CompletedTask;
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/FillOverallStatisticsOperation.cs

@@ -17,13 +17,16 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
         }
 
 
-        public Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<IStatisticsPipelineData>();
 
-            contextData.OverallStatistics = _mapper.Map<IStatistics, ShortStatistics>(contextData.History[0]);
+            if(contextData?.History != null)
+            {
+                contextData.OverallStatistics = _mapper.Map<IStatistics, ShortStatistics>(contextData.History[0]);
+            }
 
-            return next.Invoke(context);
+            return next != null ? next.Invoke(context) : Task.CompletedTask;
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/FillPeriodDifferenceOperation.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Threading.Tasks;
-using AutoMapper;
 using WotBlitzStatisticsPro.Common.Model;
 using WotBlitzStatisticsPro.Logic.AccountInformationPipeline.OperationContext;
 using WotBlitzStatisticsPro.Logic.Calculations;
@@ -10,11 +9,11 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
 {
     public class FillPeriodDifferenceOperation : IOperation<IOperationContext>
     {
-        public Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<IStatisticsPipelineData>();
 
-            if (contextData.History.Length > 1)
+            if (contextData?.History != null && contextData.History.Length > 1)
             {
                 contextData.PeriodDifference = new StatisticsDifference();
                 var historyLastIndex = contextData.History.Length - 1;
@@ -22,7 +21,7 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
                 contextData.PeriodDifference.FillDifference(contextData.History[0], contextData.History[historyLastIndex]);
             }
 
-            return next.Invoke(context);
+            return next != null ? next.Invoke(context) : Task.CompletedTask;
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/FillPeriodStatisticsOperation.cs

@@ -18,11 +18,11 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
         }
 
 
-        public Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<IStatisticsPipelineData>();
 
-            if (contextData.History.Length > 1)
+            if (contextData?.History != null && contextData.History.Length > 1)
             {
                 var diff = new AccountInfoHistory(context.Request.AccountId, contextData.History[0].LastBattleTime);
 
@@ -36,7 +36,7 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
                 contextData.PeriodAccountStatistics = _mapper.Map<IStatistics, ShortStatistics>(diff);
             }
 
-            return next.Invoke(context);
+            return next != null ? next.Invoke(context) : Task.CompletedTask;
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/FillStatisticsDifferenceOperation.cs

@@ -10,11 +10,11 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
 {
     public class FillStatisticsDifferenceOperation : IOperation<IOperationContext>
     {
-        public Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<IStatisticsPipelineData>();
 
-            if (contextData.History.Length > 1)
+            if (contextData?.History != null && contextData.History.Length > 1)
             {
                 contextData.StatisticsHistory = new StatisticsDifference[contextData.History.Length - 1];
                 for (int i = 1; i < contextData.History.Length; i++)
@@ -24,7 +24,7 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
                 }
             }
 
-            return next.Invoke(context);
+            return next != null ? next.Invoke(context) : Task.CompletedTask;
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/GetAccountInfoOperation.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Threading.Tasks;
 using AutoMapper;
+using Microsoft.Extensions.Logging;
 using WotBlitzStatisticsPro.DataAccess.Model.Accounts;
 using WotBlitzStatisticsPro.Logic.AccountInformationPipeline.OperationContext;
 using WotBlitzStatisticsPro.Logic.Pipeline;
@@ -13,29 +14,39 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
     {
         private readonly IWargamingApiClient _wargamingApi;
         private readonly IMapper _mapper;
+        private readonly ILogger<GetAccountInfoOperation> _logger;
 
         public GetAccountInfoOperation(
             IWargamingApiClient wargamingApi,
-            IMapper mapper)
+            IMapper mapper,
+            ILogger<GetAccountInfoOperation> logger)
         {
             _wargamingApi = wargamingApi;
             _mapper = mapper;
+            _logger = logger;
         }
 
-        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var accountInfo = await 
                 _wargamingApi.GetPlayerAccountInfo(context.Request.AccountId, context.Request.RealmType, context.Request.RequestLanguage);
 
+            if (accountInfo == null)
+            {
+                _logger.LogInformation(
+                    $"Account not found for AccountId {context.Request.AccountId} and {context.Request.RealmType} realm");
+                return;
+            }
+
             // Store info to AccountInfo and in AccountInfoHistory
             var contextData = context.Get<AccountInformationPipelineContextData>();
             contextData.AccountInfo = _mapper.Map<WotAccountInfo, AccountInfo>(accountInfo);
             contextData.AccountInfo.Realm = context.Request.RealmType;
 
             contextData.AccountInfoHistory = new AccountInfoHistory(context.Request.AccountId, contextData.AccountInfo.LastBattleTime);
-            _mapper.Map(accountInfo.Statistics.All, contextData.AccountInfoHistory);
+            _mapper.Map(accountInfo.Statistics?.All, contextData.AccountInfoHistory);
 
-            await next.Invoke(context);
+            if (next != null) await next.Invoke(context);
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/GetTanksInfoOperation.cs

@@ -1,12 +1,13 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
 using AutoMapper;
+using Microsoft.Extensions.Logging;
 using WotBlitzStatisticsPro.DataAccess.Model.Accounts;
 using WotBlitzStatisticsPro.Logic.AccountInformationPipeline.OperationContext;
 using WotBlitzStatisticsPro.Logic.Pipeline;
 using WotBlitzStatisticsPro.WgApiClient;
-using WotBlitzStatisticsPro.WgApiClient.Model;
 
 namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
 {
@@ -14,26 +15,36 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
     {
         private readonly IWargamingTanksApiClient _wargamingApi;
         private readonly IMapper _mapper;
+        private readonly ILogger<GetTanksInfoOperation> _logger;
 
         public GetTanksInfoOperation(
             IWargamingTanksApiClient wargamingApi,
-            IMapper mapper)
+            IMapper mapper,
+            ILogger<GetTanksInfoOperation> logger)
         {
             _wargamingApi = wargamingApi;
             _mapper = mapper;
+            _logger = logger;
         }
 
-        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<AccountInformationPipelineContextData>();
 
             var tanksInfo = await
                 _wargamingApi.GetPlayerAccountTanksInfo(context.Request.AccountId, context.Request.RealmType, context.Request.RequestLanguage);
 
+            if (tanksInfo == null)
+            {
+                _logger.LogInformation(
+                    $"Tanks not found for AccountId {context.Request.AccountId} and {context.Request.RealmType} realm");
+                return;
+            }
+
             contextData.Tanks = new List<TankInfo>();
             contextData.TanksHistory = new Dictionary<long, TankInfoHistory>();
 
-            tanksInfo.ForEach(tank =>
+            tanksInfo.OrderByDescending(t => t.LastBattleTime).ToList().ForEach(tank =>
             {
                 var tankInfo = new TankInfo(tank.AccountId, tank.TankId);
                 _mapper.Map(tank, tankInfo);
@@ -43,7 +54,7 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
                 contextData.TanksHistory[stat.TankId] = stat;
             });
 
-            await next.Invoke(context);
+            if (next != null) await next.Invoke(context);
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/ReadAccountInfoFromDbOperation.cs

@@ -15,12 +15,12 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
             _accountDataAccessor = accountDataAccessor;
         }
 
-        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<IDatabasePipelineContextData>();
 
             contextData.DbAccountInfo = await _accountDataAccessor.ReadAccountInfo(context.Request.AccountId);
-            await next.Invoke(context);
+            if (next != null) await next.Invoke(context);
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/ReadAccountInfoHistoryFromDbOperation.cs

@@ -17,12 +17,12 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
             _accountDataAccessor = accountDataAccessor;
         }
 
-        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<AccountHistoryInformationPipelineContextData>();
 
             contextData.History = (await _accountDataAccessor.GetAccountHistory(context.Request.AccountId, contextData.LastBattleSince.ToUnixTimestamp())).ToArray();
-            await next.Invoke(context);
+            if (next != null) await next.Invoke(context);
         }
     }
 }

WotBlitzStatisticsPro.Logic/AccountInformationPipeline/Operations/SaveAccountAndTanksOperation.cs

@@ -22,10 +22,18 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
             _logger = logger;
         }
 
-        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task> next)
+        public async Task Invoke(IOperationContext context, Func<IOperationContext, Task>? next)
         {
             var contextData = context.Get<AccountInformationPipelineContextData>();
 
+            if (contextData?.AccountInfo == null ||
+                contextData?.AccountInfoHistory == null ||
+                contextData?.Tanks == null ||
+                contextData?.TanksHistory == null)
+            {
+                return;
+            }
+
             await _accountDataAccessor.AddOurUpdateAccountInfo(contextData.AccountInfo);
             await _accountDataAccessor.AddAccountInfoHistory(contextData.AccountInfoHistory);
 
@@ -46,7 +54,7 @@ namespace WotBlitzStatisticsPro.Logic.AccountInformationPipeline.Operations
 
             _logger.LogInformation($"Updated account {contextData.AccountInfo.AccountId} and {tanksCount} tanks: {tankIdsAsString}");
 
-            await next.Invoke(context);
+            if (next != null) await next.Invoke(context);
         }
     }
 }

WotBlitzStatisticsPro.Logic/Dictionaries/AchievementsDictionaryUpdater.cs

@@ -21,7 +21,9 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
         [Obsolete("Parameter-less constructor only for unit tests")]
         public AchievementsDictionaryUpdater()
         {
-            
+            _wargamingDictionariesApiClient = null!;
+            _dataAccessor = null!;
+            _mapper = null!;
         }
 
         public AchievementsDictionaryUpdater(IWargamingDictionariesApiClient wargamingDictionariesApiClient, IDictionariesDataAccessor dataAccessor, IMapper mapper)
@@ -54,6 +56,10 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
             {
                 var wgAchievements =
                     await _wargamingDictionariesApiClient.GetAchievementsDictionary(defaultRealmType, requestLanguage);
+                if (wgAchievements == null)
+                {
+                    continue;
+                }
                 foreach (var wgAchievement in wgAchievements)
                 {
                     var mappedAchievement =
@@ -88,8 +94,8 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
                                         wgAchievementOption);
                                 mappedAchievement.Options.Add(mappedOption);
                             }
-                            mappedOption.Name.Add(new LocalizableString { Language = requestLanguage, Value = wgAchievement.Name });
-                            mappedOption.Description.Add(new LocalizableString { Language = requestLanguage, Value = wgAchievement.Description });
+                            mappedOption.Name?.Add(new LocalizableString { Language = requestLanguage, Value = wgAchievement.Name });
+                            mappedOption.Description?.Add(new LocalizableString { Language = requestLanguage, Value = wgAchievement.Description });
                         }
                     }
                 }

WotBlitzStatisticsPro.Logic/Dictionaries/StaticDictionariesUpdater.cs

@@ -21,7 +21,9 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
         [Obsolete("Parameter-less constructor only for unit tests")]
         public StaticDictionariesUpdater()
         {
-            
+            _wargamingDictionariesApiClient = null!;
+            _dataAccessor = null!;
+            _mapper = null!;
         }
 
         public StaticDictionariesUpdater(
@@ -42,30 +44,45 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
                 clanRoles,
                 achievementsSections) = await GetAndMapDictionaries();
 
-            await _dataAccessor.UpdateLanguages(languages);
-            await _dataAccessor.UpdateNations(nations);
-            await _dataAccessor.UpdateVehicleTypes(vehicleTypes);
-            await _dataAccessor.UpdateClanRoles(clanRoles);
-            await _dataAccessor.UpdateAchievementsSections(achievementsSections);
+            if(languages != null)
+            {
+                await _dataAccessor.UpdateLanguages(languages);
+            }
+            if(nations != null)
+            {
+                await _dataAccessor.UpdateNations(nations);
+            }
+            if(vehicleTypes != null)
+            {
+                await _dataAccessor.UpdateVehicleTypes(vehicleTypes);
+            }
+            if(clanRoles != null)
+            {
+                await _dataAccessor.UpdateClanRoles(clanRoles);
+            }
+            if(achievementsSections != null)
+            {
+                await _dataAccessor.UpdateAchievementsSections(achievementsSections);
+            }
 
             return new UpdateDictionariesResponseItem
             {
                 DictionaryType = DictionaryType.StaticDictionaries,
                 Description =
-                    $"Updated {languages.Count} items in Languages dictionary; {nations.Count} items in Nations dictionary; {vehicleTypes.Count} items in VehicleTypes dictionary; {clanRoles.Count} items in ClanRoles dictionary; {achievementsSections.Count} items in AchievementsSections dictionary"
+                    $"Updated {languages?.Count} items in Languages dictionary; {nations?.Count} items in Nations dictionary; {vehicleTypes?.Count} items in VehicleTypes dictionary; {clanRoles?.Count} items in ClanRoles dictionary; {achievementsSections?.Count} items in AchievementsSections dictionary"
             };
         }
 
         private async Task<(
-            List<ILanguageDictionary>,
-            List<INationDictionary>,
-            List<IVehicleTypeDictionary>,
-            List<IClanRoleDictionary>,
-            List<IAchievementSectionDictionary>)> GetAndMapDictionaries()
+            List<ILanguageDictionary>?,
+            List<INationDictionary>?,
+            List<IVehicleTypeDictionary>?,
+            List<IClanRoleDictionary>?,
+            List<IAchievementSectionDictionary>?)> GetAndMapDictionaries()
         {
             var defaultRealmType = RealmType.Eu;
 
-            List<ILanguageDictionary> languages = null;
+            List<ILanguageDictionary>? languages = null;
             var nations = new List<INationDictionary>();
             var vehicleTypes = new List<IVehicleTypeDictionary>();
             var clanRoles = new List<IClanRoleDictionary>();
@@ -76,17 +93,14 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
                 var (wotEncyclopediaInfoResponse, wotClanMembersDictionaryResponse) =
                     await _wargamingDictionariesApiClient.GetStaticDictionariesAsync(defaultRealmType, requestLanguage);
 
-                if (languages == null)
-                {
-                    languages =
-                        _mapper.Map<Dictionary<string, string>, List<LanguageDictionary>>(wotEncyclopediaInfoResponse
-                            .Languages).Cast<ILanguageDictionary>().ToList();
-                }
+                if (wotEncyclopediaInfoResponse?.Languages != null)
+                    languages ??= _mapper
+                        .Map<Dictionary<string, string>, List<LanguageDictionary>>(wotEncyclopediaInfoResponse.Languages).Cast<ILanguageDictionary>().ToList();
 
-                MapVehicleNations(requestLanguage, wotEncyclopediaInfoResponse.VehicleNations, nations);
-                MapVehicleTypes(requestLanguage, wotEncyclopediaInfoResponse.VehicleTypes, vehicleTypes);
-                MapClanRoles(requestLanguage, wotClanMembersDictionaryResponse.ClanRoles, clanRoles);
-                MapAchievementsSections(requestLanguage, wotEncyclopediaInfoResponse.AchievementSections, achievementsSections);
+                MapVehicleNations(requestLanguage, wotEncyclopediaInfoResponse?.VehicleNations, nations);
+                MapVehicleTypes(requestLanguage, wotEncyclopediaInfoResponse?.VehicleTypes, vehicleTypes);
+                MapClanRoles(requestLanguage, wotClanMembersDictionaryResponse?.ClanRoles, clanRoles);
+                MapAchievementsSections(requestLanguage, wotEncyclopediaInfoResponse?.AchievementSections, achievementsSections);
             }
 
             return (languages, nations, vehicleTypes, clanRoles, achievementsSections);
@@ -94,9 +108,13 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
 
         private void MapVehicleNations(
             RequestLanguage requestLanguage,
-            Dictionary<string, string> sourceDictionary,
+            Dictionary<string, string>? sourceDictionary,
             List<INationDictionary> destinationDictionary)
         {
+            if (sourceDictionary == null)
+            {
+                return;
+            }
             foreach (var source in sourceDictionary)
             {
                 var destinationItem = destinationDictionary.FirstOrDefault(d => d.NationId == source.Key);
@@ -116,9 +134,14 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
 
         private void MapVehicleTypes(
             RequestLanguage requestLanguage,
-            Dictionary<string, string> sourceDictionary,
+            Dictionary<string, string>? sourceDictionary,
             List<IVehicleTypeDictionary> destinationDictionary)
         {
+            if (sourceDictionary == null)
+            {
+                return;
+            }
+
             foreach (var source in sourceDictionary)
             {
                 var destinationItem = destinationDictionary.FirstOrDefault(d => d.VehicleTypeId == source.Key);
@@ -138,9 +161,14 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
 
         private void MapClanRoles(
             RequestLanguage requestLanguage,
-            Dictionary<string, string> sourceDictionary,
+            Dictionary<string, string>? sourceDictionary,
             List<IClanRoleDictionary> destinationDictionary)
         {
+            if (sourceDictionary == null)
+            {
+                return;
+            }
+
             foreach (var source in sourceDictionary)
             {
                 var destinationItem = destinationDictionary.FirstOrDefault(d => d.ClanRoleId == source.Key);
@@ -160,9 +188,14 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
 
         private void MapAchievementsSections(
             RequestLanguage requestLanguage,
-            Dictionary<string, WotEncyclopediaInfoAchievementSection> sourceSections,
+            Dictionary<string, WotEncyclopediaInfoAchievementSection>? sourceSections,
             List<IAchievementSectionDictionary> destinationDictionary)
         {
+            if (sourceSections == null)
+            {
+                return;
+            }
+
             foreach (var section in sourceSections)
             {
                 var destinationItem = 

WotBlitzStatisticsPro.Logic/Dictionaries/VehiclesDictionaryUpdater.cs

@@ -21,7 +21,9 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
         [Obsolete("Parameter-less constructor only for unit tests")]
         public VehiclesDictionaryUpdater()
         {
-
+            _wargamingDictionariesApiClient = null!;
+            _dataAccessor = null!;
+            _mapper = null!;
         }
 
         public VehiclesDictionaryUpdater(IWargamingDictionariesApiClient wargamingDictionariesApiClient,
@@ -57,6 +59,11 @@ namespace WotBlitzStatisticsPro.Logic.Dictionaries
                 var wgVehicles =
                     await _wargamingDictionariesApiClient.GetVehicles(defaultRealmType, requestLanguage);
 
+                if (wgVehicles == null)
+                {
+                    continue;
+                }
+
                 foreach (var wgVehicle in wgVehicles)
                 {
                     var mappedVehicle = vehicles.FirstOrDefault(v => v.TankId == wgVehicle.TankId);

WotBlitzStatisticsPro.Logic/Mappers/AccountSearchResponseProfile.cs

@@ -11,7 +11,7 @@ namespace WotBlitzStatisticsPro.Logic.Mappers
             CreateMap<WotAccountListResponse, AccountsSearchResponseItem>()
                 .ForMember(
                     d => d.AccountId, 
-                    o => o.MapFrom(s => s.AccountId.Value));
+                    o => o.MapFrom(s => s.AccountId ?? -1));
         }
     }
 }

WotBlitzStatisticsPro.Logic/Mappers/ClanSearchResponseProfile.cs

@@ -11,7 +11,7 @@ namespace WotBlitzStatisticsPro.Logic.Mappers
             CreateMap<WotClanListResponse, ClanSearchResponseItem>()
                 .ForMember(
                     d => d.ClanId,
-                    o => o.MapFrom(s => s.ClanId.Value));
+                    o => o.MapFrom(s => s.ClanId ?? -1));
 
         }
     }

WotBlitzStatisticsPro.Logic/Mappers/ShortStatisticsProfile.cs

@@ -12,11 +12,11 @@ namespace WotBlitzStatisticsPro.Logic.Mappers
                 .ForMember(d => d.LastBattleTime, 
                     o => o.MapFrom(s => s.LastBattleTime.ToDateTime()))
                 .ForMember(d => d.AvgDamage,
-                    o => o.MapFrom(s => s.Battles.HasValue && s.Battles > 0 ? ((decimal)s.DamageDealt / s.Battles) : 0m))
+                    o => o.MapFrom(s => s.Battles.HasValue && s.DamageDealt.HasValue && s.Battles > 0 ? ((decimal)s.DamageDealt / s.Battles) : 0m))
                 .ForMember(d => d.AvgXp,
-                    o => o.MapFrom(s => s.Battles.HasValue && s.Battles > 0 ? ((decimal)s.Xp / s.Battles) : 0m))
+                    o => o.MapFrom(s => s.Battles.HasValue && s.Xp.HasValue && s.Battles > 0 ? ((decimal)s.Xp / s.Battles) : 0m))
                 .ForMember(d => d.WinRate,
-                    o => o.MapFrom(s => s.Battles.HasValue && s.Battles > 0 ? (100 * (decimal)s.Wins / s.Battles) : 0m))
+                    o => o.MapFrom(s => s.Battles.HasValue && s.Wins.HasValue && s.Battles > 0 ? (100 * (decimal)s.Wins / s.Battles) : 0m))
                 ;
         }
     }

WotBlitzStatisticsPro.Logic/Mappers/VehicleDictionaryProfile.cs

@@ -22,13 +22,13 @@ namespace WotBlitzStatisticsPro.Logic.Mappers
                 .ForMember(d => d.Tier,
                     o => o.MapFrom(s => s.Tier))
                 .ForMember(d => d.PreviewImage,
-                    o => o.MapFrom(s => s.Images["preview"]))
+                    o => o.MapFrom(s => s.Images == null ? string.Empty : s.Images["preview"]))
                 .ForMember(d => d.NormalImage,
-                    o => o.MapFrom(s => s.Images["normal"]))
+                    o => o.MapFrom(s => s.Images == null ? string.Empty : s.Images["normal"]))
                 .ForMember(d => d.PriceCredit,
-                    o => o.MapFrom(s => s.Cost["price_credit"]))
+                    o => o.MapFrom(s => s.Cost == null ? string.Empty : s.Cost["price_credit"]))
                 .ForMember(d => d.PriceGold,
-                    o => o.MapFrom(s => s.Cost["price_gold"]))
+                    o => o.MapFrom(s => s.Cost == null ? string.Empty : s.Cost["price_gold"]))
                 .ForMember(d => d.NexTanksInTree,
                     o =>
                         o.MapFrom(s => s.NextTanks))

WotBlitzStatisticsPro.Logic/Pipeline/IOperation.cs

@@ -13,6 +13,6 @@ namespace WotBlitzStatisticsPro.Logic.Pipeline
         /// </summary>
         /// <param name="context">Pipeline context</param>
         /// <param name="next">Next operation</param>
-        Task Invoke(TContext context, Func<TContext, Task> next);
+        Task Invoke(TContext context, Func<TContext, Task>? next);
     }
 }

WotBlitzStatisticsPro.Logic/Pipeline/IPipeline.cs

@@ -9,7 +9,7 @@
         /// Builds the pipeline.
         /// </summary>
         /// <returns>First operation in pipeline.</returns>
-        IOperation<TContext> Build();
+        IOperation<TContext>? Build();
 
         /// <summary>
         /// Adds operation type to the pipeline

WotBlitzStatisticsPro.Logic/Pipeline/OperationMediator.cs

@@ -6,15 +6,15 @@ namespace WotBlitzStatisticsPro.Logic.Pipeline
     public class OperationMediator<TContext>: IOperation<TContext>
     {
         private readonly IOperation<TContext> _current;
-        private readonly IOperation<TContext> _next;
+        private readonly IOperation<TContext>? _next;
 
-        public OperationMediator(IOperation<TContext> current, IOperation<TContext> next)
+        public OperationMediator(IOperation<TContext> current, IOperation<TContext>? next)
         {
             _current = current ?? throw new ArgumentNullException(nameof(current));
             _next = next;
         }
 
-        public Task Invoke(TContext context, Func<TContext, Task> next)
+        public Task Invoke(TContext context, Func<TContext, Task>? next)
         {
             return _current.Invoke(context, c => _next == null ? Task.CompletedTask : _next.Invoke(c, null));
         }

WotBlitzStatisticsPro.Logic/Pipeline/Pipeline.cs

@@ -14,7 +14,7 @@ namespace WotBlitzStatisticsPro.Logic.Pipeline
             _operationFactory = operationFactory;
         }
 
-        public IOperation<TContext> Build()
+        public IOperation<TContext>? Build()
         {
             var allOperationTypes = _operations.ToArray();
             var lastOperationType = allOperationTypes.LastOrDefault();

WotBlitzStatisticsPro.Logic/Pipeline/ServiceProviderOperationFactory.cs

@@ -13,7 +13,7 @@ namespace WotBlitzStatisticsPro.Logic.Pipeline
 
         public IOperation<TContext> Create<TContext>(Type operationType)
         {
-            return _serviceProvider.GetService(operationType) as IOperation<TContext>;
+            return (_serviceProvider.GetService(operationType) as IOperation<TContext>)!;
         }
     }
 }

WotBlitzStatisticsPro.Logic/WargamingAccounts.cs

@@ -30,11 +30,15 @@ namespace WotBlitzStatisticsPro.Logic
                 .AddOperation<BuildAccountInfoResponseOperation>()
                 ;
 
-            await pipeline.Build()
-                .Invoke(context, null)
-                .ConfigureAwait(false);
+            var firstOperation = pipeline.Build();
+            if (firstOperation != null)
+            {
+                await firstOperation
+                    .Invoke(context, null)
+                    .ConfigureAwait(false);
+            }
 
-            return contextData.Response;
+            return contextData?.Response ?? new AccountInfoResponse();
         }
 
         public async Task<AccountInfoResponse> GatherAndSaveAccountInformation(RealmType realm, long accountId, RequestLanguage requestLanguage)
@@ -53,11 +57,15 @@ namespace WotBlitzStatisticsPro.Logic
                 .AddOperation<BuildAccountInfoResponseOperation>()
                 ;
 
-            await pipeline.Build()
-                .Invoke(context, null)
-                .ConfigureAwait(false);
+            var firstOperation = pipeline.Build();
+            if (firstOperation != null)
+            {
+                await firstOperation
+                    .Invoke(context, null)
+                    .ConfigureAwait(false);
+            }
 
-            return contextData.Response;
+            return contextData?.Response ?? new AccountInfoResponse();
         }
 
         public async Task<AccountInfoHistoryResponse> GetAccountInfoHistory(RealmType realm, long accountId, DateTime startDate, RequestLanguage requestLanguage)
@@ -77,11 +85,15 @@ namespace WotBlitzStatisticsPro.Logic
                 .AddOperation<FillAccountInfoHistoryResponse>()
                 ;
 
-            await pipeline.Build()
-                .Invoke(context, null)
-                .ConfigureAwait(false);
+            var firstOperation = pipeline.Build();
+            if (firstOperation != null)
+            {
+                await firstOperation
+                    .Invoke(context, null)
+                    .ConfigureAwait(false);
+            }
 
-            return contextData.Response;
+            return contextData?.Response ?? new AccountInfoHistoryResponse();
         }
     }
 }

WotBlitzStatisticsPro.Logic/WargamingSearch.cs

@@ -24,6 +24,12 @@ namespace WotBlitzStatisticsPro.Logic
             RequestLanguage language)
         {
             var response = await _wargamingApiClient.FindAccounts(accountNick, realmType, language);
+
+            if (response == null)
+            {
+                return new AccountsSearchResponse();
+            }
+
             return new AccountsSearchResponse
             {
                 AccountsCount = response.Count,
@@ -37,6 +43,12 @@ namespace WotBlitzStatisticsPro.Logic
             RequestLanguage language)
         {
             var response = await _wargamingApiClient.FindClans(searchString, realmType, language);
+
+            if (response == null)
+            {
+                return new ClanSearchResponse();
+            }
+
             return new ClanSearchResponse
             {
                 ClansCount = response.Count,

WotBlitzStatisticsPro.Logic/WotBlitzStatisticsLogicInstaller.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using AutoMapper;
 using Microsoft.Extensions.DependencyInjection;
@@ -43,17 +44,13 @@ namespace WotBlitzStatisticsPro.Logic
         {
             services.AddTransient<DictionariesUpdaterResolver>(serviceProvider => dictionaryType =>
             {
-                switch (dictionaryType)
+                return dictionaryType switch
                 {
-                    case DictionaryType.StaticDictionaries:
-                        return serviceProvider.GetService<StaticDictionariesUpdater>();
-                    case DictionaryType.Achievements:
-                        return serviceProvider.GetService<AchievementsDictionaryUpdater>();
-                    case DictionaryType.Vehicles:
-                        return serviceProvider.GetService<VehiclesDictionaryUpdater>();
-                    default:
-                        return null;
-                }
+                    DictionaryType.StaticDictionaries => serviceProvider.GetService<StaticDictionariesUpdater>()!,
+                    DictionaryType.Achievements => serviceProvider.GetService<AchievementsDictionaryUpdater>()!,
+                    DictionaryType.Vehicles => serviceProvider.GetService<VehiclesDictionaryUpdater>()!,
+                    _ => throw new ApplicationException($"Unknown dictionary type '{dictionaryType}'")
+                };
             });
         }
 

WotBlitzStatisticsPro.Logic/WotBlitzStatisticsPro.Logic.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net5.0</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

WotBlitzStatisticsPro.WgApiClient/IWargamingApiClient.cs

@@ -7,23 +7,23 @@ namespace WotBlitzStatisticsPro.WgApiClient
 {
 	public interface IWargamingApiClient
 	{
-		Task<List<WotAccountListResponse>> FindAccounts(string nickName,
+		Task<List<WotAccountListResponse>?> FindAccounts(string nickName,
 			RealmType realmType = RealmType.Ru,
 			RequestLanguage language = RequestLanguage.En);
 
-		Task<List<WotClanListResponse>> FindClans(string searchString,
+		Task<List<WotClanListResponse>?> FindClans(string searchString,
 			RealmType realmType = RealmType.Ru,
 			RequestLanguage language = RequestLanguage.En);
 
-		Task<WotAccountInfo> GetPlayerAccountInfo(long accountId,
+		Task<WotAccountInfo?> GetPlayerAccountInfo(long accountId,
 			RealmType realmType = RealmType.Ru,
 			RequestLanguage language = RequestLanguage.En);
 
-		Task<ClanAccountInfo> GetPlayerClanInfo(long accountId,
+		Task<ClanAccountInfo?> GetPlayerClanInfo(long accountId,
 			RealmType realmType = RealmType.Ru,
 			RequestLanguage language = RequestLanguage.En);
 
-		Task<ClanInfo> GetClanInfo(long clanId,
+		Task<ClanInfo?> GetClanInfo(long clanId,
 			RealmType realmType = RealmType.Ru,
 			RequestLanguage language = RequestLanguage.En);
 	}

WotBlitzStatisticsPro.WgApiClient/IWargamingDictionariesApiClient.cs

@@ -8,16 +8,16 @@ namespace WotBlitzStatisticsPro.WgApiClient
     public interface IWargamingDictionariesApiClient
     {
         Task<(
-            WotEncyclopediaInfoResponse,
-            WotClanMembersDictionaryResponse)> GetStaticDictionariesAsync(
+            WotEncyclopediaInfoResponse?,
+            WotClanMembersDictionaryResponse?)> GetStaticDictionariesAsync(
             RealmType realmType = RealmType.Ru,
             RequestLanguage language = RequestLanguage.En);
 
-        Task<List<WotEncyclopediaAchievementsResponse>> GetAchievementsDictionary(
+        Task<List<WotEncyclopediaAchievementsResponse>?> GetAchievementsDictionary(
             RealmType realmType = RealmType.Ru,
             RequestLanguage language = RequestLanguage.En);
 
-        Task<List<WotEncyclopediaVehiclesResponse>> GetVehicles(
+        Task<List<WotEncyclopediaVehiclesResponse>?> GetVehicles(
             RealmType realmType = RealmType.Ru,
             RequestLanguage language = RequestLanguage.En);
     }

WotBlitzStatisticsPro.WgApiClient/IWargamingTanksApiClient.cs

@@ -7,7 +7,7 @@ namespace WotBlitzStatisticsPro.WgApiClient
 {
     public interface IWargamingTanksApiClient
     {
-        Task<List<WotAccountTanksStatistics>> GetPlayerAccountTanksInfo(long accountId,
+        Task<List<WotAccountTanksStatistics>?> GetPlayerAccountTanksInfo(long accountId,
             RealmType realmType = RealmType.Ru,
             RequestLanguage language = RequestLanguage.En);
     }

WotBlitzStatisticsPro.WgApiClient/Model/ClanAccountInfo.cs

@@ -14,7 +14,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Account nick
 		///</summary>
 		[JsonProperty("account_name")]
-		public string AccountName { get; set; }
+		public string? AccountName { get; set; }
 
 		///<summary>
 		/// ClanId
@@ -32,7 +32,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Player clan role
 		///</summary>
 		[JsonProperty("role")]
-		public string Role { get; set; }
+		public string? Role { get; set; }
 
 	}
 }

WotBlitzStatisticsPro.WgApiClient/Model/ClanInfo.cs

@@ -22,7 +22,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Clan color in HEX #RRGGBB
 		///</summary>
 		[JsonProperty("color")]
-		public string Color { get; set; }
+		public string? Color { get; set; }
 
 		///<summary>
 		/// Date of clan creation
@@ -40,25 +40,25 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Clan creator nick
 		///</summary>
 		[JsonProperty("creator_name")]
-		public string CreatorName { get; set; }
+		public string? CreatorName { get; set; }
 
 		///<summary>
 		/// Clan description
 		///</summary>
 		[JsonProperty("description")]
-		public string Description { get; set; }
+		public string? Description { get; set; }
 
 		///<summary>
 		/// Html Clan description 
 		///</summary>
 		[JsonProperty("description_html")]
-		public string DescriptionHtml { get; set; }
+		public string? DescriptionHtml { get; set; }
 
 		///<summary>
 		/// Is clan deleted. Actual info about deleted clan only in fields: clan_id, is_clan_disbanded, updated_at.
 		///</summary>
 		[JsonProperty("is_clan_disbanded")]
-		public bool IsClanDisbanded { get; set; }
+		public bool? IsClanDisbanded { get; set; }
 
 		///<summary>
 		/// Clan commander accountId
@@ -70,7 +70,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Clan commander nick
 		///</summary>
 		[JsonProperty("leader_name")]
-		public string LeaderName { get; set; }
+		public string? LeaderName { get; set; }
 
 		///<summary>
 		/// Clan members count
@@ -82,25 +82,25 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Clan motto
 		///</summary>
 		[JsonProperty("motto")]
-		public string Motto { get; set; }
+		public string? Motto { get; set; }
 
 		///<summary>
 		/// Clan name
 		///</summary>
 		[JsonProperty("name")]
-		public string Name { get; set; }
+		public string? Name { get; set; }
 
 		///<summary>
 		/// Renamed clan name
 		///</summary>
 		[JsonProperty("old_name")]
-		public string OldName { get; set; }
+		public string? OldName { get; set; }
 
 		///<summary>
 		/// Renamed clan tag
 		///</summary>
 		[JsonProperty("old_tag")]
-		public string OldTag { get; set; }
+		public string? OldTag { get; set; }
 
 		///<summary>
 		/// Clan renaming time in UTC
@@ -112,7 +112,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Clan tag
 		///</summary>
 		[JsonProperty("tag")]
-		public string Tag { get; set; }
+		public string? Tag { get; set; }
 
 		///<summary>
 		/// Clan info updated at
@@ -124,19 +124,19 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Clan emblems info
 		///</summary>
 		[JsonProperty("emblems")]
-		public WgnClansInfoEmblems Emblems { get; set; }
+		public WgnClansInfoEmblems? Emblems { get; set; }
 
 		///<summary>
 		/// Clan members information. Depends on members_key field in request.
 		///</summary>
 		[JsonProperty("members")]
-		public WgnClansInfoMembers Members { get; set; }
+		public WgnClansInfoMembers? Members { get; set; }
 
 		///<summary>
 		/// Private clan info
 		///</summary>
 		[JsonProperty("private")]
-		public WgnClansInfoPrivate Private { get; set; }
+		public WgnClansInfoPrivate? Private { get; set; }
 	}
 
     public class WgnClansInfoEmblems
@@ -145,31 +145,31 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
         /// 195x195 px Icons list
         ///</summary>
         [JsonProperty("x195")]
-        public Dictionary<string, string> X195 { get; set; }
+        public Dictionary<string, string>? X195 { get; set; }
 
 		///<summary>
 		/// 24x24 px Icons list
 		///</summary>
 		[JsonProperty("x24")]
-        public Dictionary<string, string> X24 { get; set; }
+        public Dictionary<string, string>? X24 { get; set; }
 
 		///<summary>
 		/// 256x256 px Icons list
 		///</summary>
 		[JsonProperty("x256")]
-        public Dictionary<string, string> X256 { get; set; }
+        public Dictionary<string, string>? X256 { get; set; }
 
 		///<summary>
 		///  32x32 px Icons list
 		///</summary>
 		[JsonProperty("x32")]
-        public Dictionary<string, string> X32 { get; set; }
+        public Dictionary<string, string>? X32 { get; set; }
 
 		///<summary>
 		/// 64x64 px Icons list
 		///</summary>
 		[JsonProperty("x64")]
-        public Dictionary<string, string> X64 { get; set; }
+        public Dictionary<string, string>? X64 { get; set; }
 	}
 
     public class WgnClansInfoMembers
@@ -184,7 +184,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
         /// Clan member nick
         ///</summary>
         [JsonProperty("account_name")]
-        public string AccountName { get; set; }
+        public string? AccountName { get; set; }
 
         ///<summary>
         /// Date of joining the clan
@@ -196,19 +196,19 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
         /// Clan member role
         ///</summary>
         [JsonProperty("role")]
-        public string Role { get; set; }
+        public string? Role { get; set; }
 
         ///<summary>
         /// Localized member role
         ///</summary>
         [JsonProperty("role_i18n")]
-        public string RoleI18n { get; set; }
+        public string? RoleI18n { get; set; }
 	}
 
     public class WgnClansInfoPrivate
     {
         [JsonProperty("online_members")]
-        public int[] OnlineMembers { get; set; }
+        public int[]? OnlineMembers { get; set; }
 
         [JsonProperty("treasury")]
         public long? Treasury { get; set; }

WotBlitzStatisticsPro.WgApiClient/Model/WotAccountInfo.cs

@@ -26,7 +26,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Player's nick
 		///</summary>
 		[JsonProperty("nickname")]
-		public string Nickname { get; set; }
+		public string? Nickname { get; set; }
 
 		///<summary>
 		/// Player information update date
@@ -38,12 +38,12 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Private account data
 		///</summary>
 		[JsonProperty("private")]
-		public WotAccountPrivateInfo Private { get; set; }
+		public WotAccountPrivateInfo? Private { get; set; }
 
 		///<summary>
 		/// Player's statistics
 		///</summary>
 		[JsonProperty("statistics")]
-		public WotAccountStatistics Statistics { get; set; }
+		public WotAccountStatistics? Statistics { get; set; }
 	}
 }

WotBlitzStatisticsPro.WgApiClient/Model/WotAccountListResponse.cs

@@ -14,6 +14,6 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
         /// Player nick
         ///</summary>
         [JsonProperty("nickname")]
-        public string Nickname { get; set; }
+        public string? Nickname { get; set; }
 	}
 }

WotBlitzStatisticsPro.WgApiClient/Model/WotAccountPrivateInfo.cs

@@ -8,7 +8,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Account ban info
 		///</summary>
 		[JsonProperty("ban_info")]
-		public string BanInfo { get; set; }
+		public string? BanInfo { get; set; }
 
 		///<summary>
 		/// Account ban expiration date
@@ -47,23 +47,22 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		public bool IsPremium { get; set; }
 
 		///<summary>
-		/// Premium accunt expiration time
+		/// Premium account expiration time
 		///</summary>
 		[JsonProperty("premium_expires_at")]
 		private int? PremiumExpiresAt { get; set; }
 
 		///<summary>
-		///Группы контактов.
-		///Дополнительное поле.
+		/// Group of contacts.
 		///</summary>
 		[JsonProperty("grouped_contacts")]
-		public WotAccountPrivateInfoGroupedContacts GroupedContacts { get; set; }
+		public WotAccountPrivateInfoGroupedContacts? GroupedContacts { get; set; }
 
 		///<summary>
-		///Ограничения аккаунта
+		/// Account restrictions
 		///</summary>
 		[JsonProperty("restrictions")]
-		public WotAccountPrivateInfoRestrictions Restrictions { get; set; }
+		public WotAccountPrivateInfoRestrictions? Restrictions { get; set; }
 
 	}
 }

WotBlitzStatisticsPro.WgApiClient/Model/WotAccountPrivateInfoGroupedContacts.cs

@@ -9,18 +9,18 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Blocked accountIds
 		///</summary>
 		[JsonProperty("blocked")]
-		public int[] Blocked { get; set; }
+		public int[]? Blocked { get; set; }
 
 		///<summary>
 		/// Groups
 		///</summary>
 		[JsonProperty("groups")]
-		public Dictionary<string, string> Groups { get; set; }
+		public Dictionary<string, string>? Groups { get; set; }
 
 		///<summary>
 		/// Ungrouped accountIds
 		///</summary>
 		[JsonProperty("ungrouped")]
-		public int[] Ungrouped { get; set; }
+		public int[]? Ungrouped { get; set; }
 	}
 }

WotBlitzStatisticsPro.WgApiClient/Model/WotAccountStatistics.cs

@@ -9,12 +9,12 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Amount of destroyed by player tanks.
 		///</summary>
 		[JsonProperty("frags")]
-		public Dictionary<string, string> Frags { get; set; }
+		public Dictionary<string, string>? Frags { get; set; }
 
 		///<summary>
 		/// Full player's statistics
 		///</summary>
 		[JsonProperty("all")]
-		public WotAccountFullStatistics All { get; set; }
+		public WotAccountFullStatistics? All { get; set; }
 	}
 }

WotBlitzStatisticsPro.WgApiClient/Model/WotAccountTanksStatistics.cs

@@ -50,10 +50,10 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
         /// Whole statistics
         ///</summary>
         [JsonProperty("all")]
-        public WotAccountTanksFullStatistics All { get; set; }
+        public WotAccountTanksFullStatistics? All { get; set; }
 
         [JsonProperty("frags")]
-        public Dictionary<string, string> Frags { get; set; }
+        public Dictionary<string, string>? Frags { get; set; }
 
 	}
 }

WotBlitzStatisticsPro.WgApiClient/Model/WotClanListResponse.cs

@@ -14,13 +14,13 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
         /// Clan Tag
         ///</summary>
         [JsonProperty("tag")]
-        public string Tag { get; set; }
+        public string? Tag { get; set; }
 
         ///<summary>
         /// Clan Name
         ///</summary>
         [JsonProperty("name")]
-        public string Name { get; set; }
+        public string? Name { get; set; }
 
         ///<summary>
         /// Clan created at. (UNIX Epoch time)

WotBlitzStatisticsPro.WgApiClient/Model/WotClanMembersDictionaryResponse.cs

@@ -9,12 +9,12 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
         /// Clan roles list
         /// </summary>
         [JsonProperty("clans_roles")]
-        public Dictionary<string, string> ClanRoles { get; set; }
+        public Dictionary<string, string>? ClanRoles { get; set; }
 
         /// <summary>
         /// Clan settings list
         /// </summary>
         [JsonProperty("settings")]
-        public Dictionary<string, string> Settings { get; set; }
+        public Dictionary<string, string>? Settings { get; set; }
     }
 }

WotBlitzStatisticsPro.WgApiClient/Model/WotEncyclopediaAchievementsResponse.cs

@@ -6,43 +6,43 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
     public class WotEncyclopediaAchievementsResponse
     {
 		[JsonProperty("achievement_id")]
-		public string AchievementId { get; set; }
+		public string? AchievementId { get; set; }
 
 		///<summary>
 		/// Achievement condition
 		///</summary>
 		[JsonProperty("condition")]
-		public string Condition { get; set; }
+		public string? Condition { get; set; }
 
 		///<summary>
 		/// Achievement description
 		///</summary>
 		[JsonProperty("description")]
-		public string Description { get; set; }
+		public string? Description { get; set; }
 
 		///<summary>
 		/// Historical info
 		///</summary>
 		[JsonProperty("hero_info")]
-		public string HeroInfo { get; set; }
+		public string? HeroInfo { get; set; }
 
 		///<summary>
 		/// Image link
 		///</summary>
 		[JsonProperty("image")]
-		public string Image { get; set; }
+		public string? Image { get; set; }
 
 		///<summary>
 		/// Image 180x180px link
 		///</summary>
 		[JsonProperty("image_big")]
-		public string ImageBig { get; set; }
+		public string? ImageBig { get; set; }
 
 		///<summary>
 		/// Achievement name
 		///</summary>
 		[JsonProperty("name")]
-		public string Name { get; set; }
+		public string? Name { get; set; }
 
 		///<summary>
 		/// Sort order
@@ -60,7 +60,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Achievement section
 		///</summary>
 		[JsonProperty("section")]
-		public string Section { get; set; }
+		public string? Section { get; set; }
 
 		///<summary>
 		/// Achievement section order
@@ -72,13 +72,13 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Achievement Type
 		///</summary>
 		[JsonProperty("type")]
-		public string Type { get; set; }
+		public string? Type { get; set; }
 
 		///<summary>
 		/// Achievement options
 		///</summary>
 		[JsonProperty("options")]
-		public WotEncyclopediaAchievementsOptions[] Options { get; set; }
+		public WotEncyclopediaAchievementsOptions[]? Options { get; set; }
 	}
 
 	public class WotEncyclopediaAchievementsOptions
@@ -88,21 +88,21 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Achievement description
 		///</summary>
 		[JsonProperty("description")]
-		public string Description { get; set; }
+		public string? Description { get; set; }
 
 		///<summary>
 		/// Image link
 		///</summary>
 		[JsonProperty("image")]
-		public string Image { get; set; }
+		public string? Image { get; set; }
 
 		///<summary>
 		/// Image 180x180px link
 		///</summary>
 		[JsonProperty("image_big")]
-		public string ImageBig { get; set; }
+		public string? ImageBig { get; set; }
 
 		[JsonProperty("name")]
-		public string Name { get; set; }
+		public string? Name { get; set; }
 	}
 }

WotBlitzStatisticsPro.WgApiClient/Model/WotEncyclopediaInfoResponse.cs

@@ -10,13 +10,13 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
         /// Game client version
         ///</summary>
         [JsonProperty("game_version")]
-        public string GameVersion { get; set; }
+        public string? GameVersion { get; set; }
 
         ///<summary>
         /// List of supported languages
         ///</summary>
         [JsonProperty("languages")]
-        public Dictionary<string, string> Languages { get; set; }
+        public Dictionary<string, string>? Languages { get; set; }
 
         ///<summary>
         /// Encyclopedia last update time
@@ -28,25 +28,25 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
         /// Cru clan role
         ///</summary>
         [JsonProperty("vehicle_crew_roles")]
-        public Dictionary<string, string> VehicleCrewRoles { get; set; }
+        public Dictionary<string, string>? VehicleCrewRoles { get; set; }
 
         ///<summary>
         /// Vehicle nations dictionary
         ///</summary>
         [JsonProperty("vehicle_nations")]
-        public Dictionary<string, string> VehicleNations { get; set; }
+        public Dictionary<string, string>? VehicleNations { get; set; }
 
         ///<summary>
         /// Vehicle types dictionary
         ///</summary>
         [JsonProperty("vehicle_types")]
-        public Dictionary<string, string> VehicleTypes { get; set; }
+        public Dictionary<string, string>? VehicleTypes { get; set; }
 
         ///<summary>
         /// Achievements sections
         ///</summary>
         [JsonProperty("achievement_sections")]
-        public Dictionary<string, WotEncyclopediaInfoAchievementSection> AchievementSections { get; set; }
+        public Dictionary<string, WotEncyclopediaInfoAchievementSection>? AchievementSections { get; set; }
 
 	}
 
@@ -57,7 +57,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
         /// Achievements section name
         ///</summary>
         [JsonProperty("name")]
-        public string Name { get; set; }
+        public string? Name { get; set; }
 
         ///<summary>
         /// Achievement section order

WotBlitzStatisticsPro.WgApiClient/Model/WotEncyclopediaVehiclesResponse.cs

@@ -9,19 +9,19 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Vehicle description
 		///</summary>
 		[JsonProperty("description")]
-		public string Description { get; set; }
+		public string? Description { get; set; }
 
 		///<summary>
 		/// Engines id list
 		///</summary>
 		[JsonProperty("engines")]
-		public int[] Engines { get; set; }
+		public int[]? Engines { get; set; }
 
 		///<summary>
 		/// Guns id list
 		///</summary>
 		[JsonProperty("guns")]
-		public int[] Guns { get; set; }
+		public int[]? Guns { get; set; }
 
 		///<summary>
 		/// Is vehicle premium
@@ -33,13 +33,13 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Vehicle name
 		///</summary>
 		[JsonProperty("name")]
-		public string Name { get; set; }
+		public string? Name { get; set; }
 
 		///<summary>
 		/// Vehicle nationId
 		///</summary>
 		[JsonProperty("nation")]
-		public string Nation { get; set; }
+		public string? Nation { get; set; }
 
 		///<summary>
 		/// List of next vehicles in tree:
@@ -48,26 +48,26 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// value - amount of XP to open it
 		///</summary>
 		[JsonProperty("next_tanks")]
-		public Dictionary<string, string> NextTanks { get; set; }
+		public Dictionary<string, string>? NextTanks { get; set; }
 
 		///<summary>
 		/// Vehicle cost by pairs
 		/// with keys: price_credit, price_gold
 		///</summary>
 		[JsonProperty("cost")]
-		public Dictionary<string, string> Cost { get; set; }
+		public Dictionary<string, string>? Cost { get; set; }
 
         ///<summary>
 		/// Price in XP for parent vehicle as key
 		///</summary>
 		[JsonProperty("prices_xp")]
-		public Dictionary<string, string> PricesXp { get; set; }
+		public Dictionary<string, string>? PricesXp { get; set; }
 
 		///<summary>
 		/// List of compatible suspensions
 		///</summary>
 		[JsonProperty("suspensions")]
-		public int[] Suspensions { get; set; }
+		public int[]? Suspensions { get; set; }
 
 		///<summary>
 		/// VehicleId
@@ -85,13 +85,13 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// List of compatible turrets ids
 		///</summary>
 		[JsonProperty("turrets")]
-		public int[] Turrets { get; set; }
+		public int[]? Turrets { get; set; }
 
 		///<summary>
 		/// Vehicle type id
 		///</summary>
 		[JsonProperty("type")]
-		public string Type { get; set; }
+		public string? Type { get; set; }
 
 		/////<summary>
 		///// Default vehicle profile
@@ -104,7 +104,7 @@ namespace WotBlitzStatisticsPro.WgApiClient.Model
 		/// Keys: preview, normal
 		///</summary>
 		[JsonProperty("images")]
-		public Dictionary<string, string> Images { get; set; }
+		public Dictionary<string, string>? Images { get; set; }
 
 		/////<summary>
 		///// Information about investigated modules

WotBlitzStatisticsPro.WgApiClient/ResponseBody.cs

@@ -1,20 +1,22 @@
-using Newtonsoft.Json;
+using System.ComponentModel.DataAnnotations;
+using System.Diagnostics.CodeAnalysis;
+using Newtonsoft.Json;
 
 namespace WotBlitzStatisticsPro.WgApiClient
 {
-	internal class ResponseBody<T>
+	internal class ResponseBody<T> where T: class
 	{
 		[JsonProperty("status")]
-		public string Status { get; set; }
+		public string? Status { get; set; }
 
 		[JsonProperty("meta")]
-		public Meta Meta { get; set; }
+		public Meta? Meta { get; set; }
 
 		[JsonProperty("data")]
-		public T Data { get; set; }
+		public T? Data { get; set; }
 
 		[JsonProperty("error")]
-		public Error Error { get; set; }
+		public Error? Error { get; set; }
 	}
 
 	internal class Meta
@@ -26,15 +28,15 @@ namespace WotBlitzStatisticsPro.WgApiClient
 	internal class Error
 	{
 		[JsonProperty("field")]
-		public string Field { get; set; }
+		public string? Field { get; set; }
 
 		[JsonProperty("message")]
-		public string Message { get; set; }
+		public string? Message { get; set; }
 
 		[JsonProperty("code")]
-		public string Code { get; set; }
+		public string? Code { get; set; }
 
 		[JsonProperty("value")]
-		public string Value { get; set; }
+		public string? Value { get; set; }
 	}
 }

WotBlitzStatisticsPro.WgApiClient/WagramingApiClientBase.cs

@@ -1,6 +1,7 @@
 using Newtonsoft.Json;
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Net.Http;
 using System.Net.Http.Headers;
 using System.Text;
@@ -36,11 +37,11 @@ namespace WotBlitzStatisticsPro.WgApiClient
 			_wotApiUrls[RealmType.Asia] = "https://api.worldoftanks.asia/wot/";
 		}
 
-		protected async Task<T> GetFromBlitzApi<T>(
+		protected async Task<T?> GetFromBlitzApi<T>(
 			RealmType realmType,
 			RequestLanguage language,
 			string method,
-			params string[] queryParameters)
+			params string[] queryParameters) where T: class
 		{
 			string uri = GetUri(realmType, language, method, queryParameters);
 
@@ -52,18 +53,20 @@ namespace WotBlitzStatisticsPro.WgApiClient
 			var responseString = await response.Content.ReadAsStringAsync();
 
 			var responseBody = JsonConvert.DeserializeObject<ResponseBody<T>>(responseString);
-			if (responseBody.Status == "ok")
-			{
-				return responseBody.Data;
-			}
-			if (responseBody.Status == "error")
-			{
-				var error = responseBody.Error;
-				var message = $"Field:{error.Field}  Message:{error.Message}  Value:{error.Value}  Code:{error.Code}";
-				throw new ArgumentException(message);
-			}
-			return default(T);
-		}
+			switch (responseBody.Status)
+            {
+                case "ok":
+                    return responseBody.Data;
+                case "error":
+                {
+                    var error = responseBody.Error;
+                    var message = $"Field:{(error?.Field ?? "undefined")}  Message:{(error?.Message ?? "undefined")}  Value:{(error?.Value ?? "undefined")}  Code:{(error?.Code ?? "undefined")}";
+                    throw new ArgumentException(message);
+                }
+                default:
+                    throw new ArgumentException($"Unexpected response body status '{responseBody.Status}'");
+            }
+        }
 
 		private string GetUri(RealmType realmType, RequestLanguage language, string method, string[] queryParameters)
 		{

WotBlitzStatisticsPro.WgApiClient/WargamingApiClient.cs

@@ -20,7 +20,7 @@ namespace WotBlitzStatisticsPro.WgApiClient
 		}
 
         #region Search methods
-        public async Task<List<WotAccountListResponse>> FindAccounts(string nickName,
+        public async Task<List<WotAccountListResponse>?> FindAccounts(string nickName,
 			RealmType realmType = RealmType.Ru,
 			RequestLanguage language = RequestLanguage.En)
 		{
@@ -31,7 +31,7 @@ namespace WotBlitzStatisticsPro.WgApiClient
                 $"search={nickName}").ConfigureAwait(false);
         }
 
-        public async Task<List<WotClanListResponse>> FindClans(string searchString, 
+        public async Task<List<WotClanListResponse>?> FindClans(string searchString, 
             RealmType realmType = RealmType.Ru, 
             RequestLanguage language = RequestLanguage.En)
         {
@@ -47,8 +47,8 @@ namespace WotBlitzStatisticsPro.WgApiClient
         #region Encyclopedia methods
 
         public async Task<(
-            WotEncyclopediaInfoResponse,
-            WotClanMembersDictionaryResponse)> GetStaticDictionariesAsync(
+            WotEncyclopediaInfoResponse?,
+            WotClanMembersDictionaryResponse?)> GetStaticDictionariesAsync(
                 RealmType realmType = RealmType.Ru,
                 RequestLanguage language = RequestLanguage.En)
         {
@@ -67,24 +67,24 @@ namespace WotBlitzStatisticsPro.WgApiClient
             return (encyclopedia, clanGlossaryResponse);
         }
 
-        public async Task<List<WotEncyclopediaAchievementsResponse>> GetAchievementsDictionary(RealmType realmType = RealmType.Ru, RequestLanguage language = RequestLanguage.En)
+        public async Task<List<WotEncyclopediaAchievementsResponse>?> GetAchievementsDictionary(RealmType realmType = RealmType.Ru, RequestLanguage language = RequestLanguage.En)
         {
             var response = await GetFromBlitzApi<Dictionary<string, WotEncyclopediaAchievementsResponse>>(
                 realmType,
                 language,
                 "encyclopedia/achievements/").ConfigureAwait(false);
 
-            return response.Values.ToList();
+            return response?.Values.ToList();
         }
 
-        public async Task<List<WotEncyclopediaVehiclesResponse>> GetVehicles(RealmType realmType = RealmType.Ru, RequestLanguage language = RequestLanguage.En)
+        public async Task<List<WotEncyclopediaVehiclesResponse>?> GetVehicles(RealmType realmType = RealmType.Ru, RequestLanguage language = RequestLanguage.En)
         {
             var response = await GetFromBlitzApi<Dictionary<string, WotEncyclopediaVehiclesResponse>>(
                 realmType,
                 language,
                 "encyclopedia/vehicles/").ConfigureAwait(false);
 
-            return response.Values.ToList();
+            return response?.Values.ToList();
         }
 
         #endregion
@@ -94,7 +94,7 @@ namespace WotBlitzStatisticsPro.WgApiClient
 
 
 
-        public async Task<WotAccountInfo> GetPlayerAccountInfo(long accountId,
+        public async Task<WotAccountInfo?> GetPlayerAccountInfo(long accountId,
 			RealmType realmType = RealmType.Ru,
 			RequestLanguage language = RequestLanguage.En)
 		{
@@ -103,10 +103,10 @@ namespace WotBlitzStatisticsPro.WgApiClient
 				language,
 				"account/info/",
 				$"account_id={accountId}").ConfigureAwait(false);
-			return account[accountId.ToString()];
+			return account?[accountId.ToString()];
 		}
 
-		public async Task<ClanAccountInfo> GetPlayerClanInfo(long accountId,
+		public async Task<ClanAccountInfo?> GetPlayerClanInfo(long accountId,
 			RealmType realmType = RealmType.Ru,
 			RequestLanguage language = RequestLanguage.En)
 		{
@@ -115,14 +115,14 @@ namespace WotBlitzStatisticsPro.WgApiClient
 				language,
 				"clans/accountinfo/",
 				$"account_id={accountId}").ConfigureAwait(false);
-			if (clanInfo.ContainsKey(accountId.ToString()))
+			if (clanInfo != null && clanInfo.ContainsKey(accountId.ToString()))
 			{
 				return clanInfo[accountId.ToString()];
 			}
 			return null;
 		}
 
-        public async Task<ClanInfo> GetClanInfo(
+        public async Task<ClanInfo?> GetClanInfo(
             long clanId, 
             RealmType realmType = RealmType.Ru, 
             RequestLanguage language = RequestLanguage.En)
@@ -132,7 +132,7 @@ namespace WotBlitzStatisticsPro.WgApiClient
                 language,
 				"clans/info/",
                 $"clan_id={clanId}").ConfigureAwait(false);
-            if (clanInfo.ContainsKey(clanId.ToString()))
+            if (clanInfo != null && clanInfo.ContainsKey(clanId.ToString()))
             {
                 return clanInfo[clanId.ToString()];
             }
@@ -144,7 +144,7 @@ namespace WotBlitzStatisticsPro.WgApiClient
 
         #region Tanks methods
 
-        public async Task<List<WotAccountTanksStatistics>> GetPlayerAccountTanksInfo(
+        public async Task<List<WotAccountTanksStatistics>?> GetPlayerAccountTanksInfo(
             long accountId, 
             RealmType realmType = RealmType.Ru,
             RequestLanguage language = RequestLanguage.En)
@@ -154,7 +154,7 @@ namespace WotBlitzStatisticsPro.WgApiClient
                 language,
                 "tanks/stats/",
                 $"account_id={accountId}").ConfigureAwait(false);
-            return tanks[accountId.ToString()] ?? new List<WotAccountTanksStatistics>();
+            return tanks?[accountId.ToString()] ?? new List<WotAccountTanksStatistics>();
         }
 
         #endregion

WotBlitzStatisticsPro.WgApiClient/WotBlitzStatisticsPro.WgApiClient.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>net5.0</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>