- Made the project compatible with C# 7.3

Discord.NET/Discord.Net.Core/Net/BucketId.cs

@@ -56,7 +56,7 @@ namespace Discord.Net
         public static BucketId Create(string httpMethod, string endpoint, Dictionary<string, string> majorParams)
         {
             Preconditions.NotNullOrWhitespace(endpoint, nameof(endpoint));
-            majorParams ??= new Dictionary<string, string>();
+            majorParams = majorParams ?? new Dictionary<string, string>();
             return new BucketId(httpMethod, endpoint, majorParams, null);
         }
 

Discord.NET/Discord.Net.Core/Utils/Comparers.cs

@@ -11,23 +11,23 @@ namespace Discord
         /// <summary>
         ///     Gets an <see cref="IEqualityComparer{T}"/> to be used to compare users.
         /// </summary>
-        public static IEqualityComparer<IUser> UserComparer => _userComparer ??= new EntityEqualityComparer<IUser, ulong>();
+        public static IEqualityComparer<IUser> UserComparer => _userComparer =_userComparer ?? new EntityEqualityComparer<IUser, ulong>();
         /// <summary>
         ///     Gets an <see cref="IEqualityComparer{T}"/> to be used to compare guilds.
         /// </summary>
-        public static IEqualityComparer<IGuild> GuildComparer => _guildComparer ??= new EntityEqualityComparer<IGuild, ulong>();
+        public static IEqualityComparer<IGuild> GuildComparer => _guildComparer = _guildComparer ?? new EntityEqualityComparer<IGuild, ulong>();
         /// <summary>
         ///     Gets an <see cref="IEqualityComparer{T}"/> to be used to compare channels.
         /// </summary>
-        public static IEqualityComparer<IChannel> ChannelComparer => _channelComparer ??= new EntityEqualityComparer<IChannel, ulong>();
+        public static IEqualityComparer<IChannel> ChannelComparer => _channelComparer = _channelComparer ?? new EntityEqualityComparer<IChannel, ulong>();
         /// <summary>
         ///     Gets an <see cref="IEqualityComparer{T}"/> to be used to compare roles.
         /// </summary>
-        public static IEqualityComparer<IRole> RoleComparer => _roleComparer ??= new EntityEqualityComparer<IRole, ulong>();
+        public static IEqualityComparer<IRole> RoleComparer => _roleComparer = _roleComparer ?? new EntityEqualityComparer<IRole, ulong>();
         /// <summary>
         ///     Gets an <see cref="IEqualityComparer{T}"/> to be used to compare messages.
         /// </summary>
-        public static IEqualityComparer<IMessage> MessageComparer => _messageComparer ??= new EntityEqualityComparer<IMessage, ulong>();
+        public static IEqualityComparer<IMessage> MessageComparer => _messageComparer = _messageComparer ?? new EntityEqualityComparer<IMessage, ulong>();
 
         private static IEqualityComparer<IUser> _userComparer;
         private static IEqualityComparer<IGuild> _guildComparer;
@@ -41,13 +41,11 @@ namespace Discord
         {
             public override bool Equals(TEntity x, TEntity y)
             {
-                return (x, y) switch
-                {
-                    (null, null) => true,
-                    (null, _)    => false,
-                    (_, null)    => false,
-                    var (l, r)   => l.Id.Equals(r.Id)
-                };
+                if (x == null && y == null) return true;
+                if (x == null && y != null) return false;
+                if (x != null && y == null) return false;
+                var tuple = new Tuple<TEntity, TEntity>(x, y);
+                return tuple.Item1.Id.Equals(tuple.Item2.Id);
             }
 
             public override int GetHashCode(TEntity obj)

Discord.NET/Discord.Net.Rest/DiscordRestApiClient.cs

@@ -80,13 +80,17 @@ namespace Discord.API
         /// <exception cref="ArgumentException">Unknown OAuth token type.</exception>
         internal static string GetPrefixedToken(TokenType tokenType, string token)
         {
-            return tokenType switch
-            {
-                default(TokenType) => token,
-                TokenType.Bot => $"Bot {token}",
-                TokenType.Bearer => $"Bearer {token}",
-                _ => throw new ArgumentException(message: "Unknown OAuth token type.", paramName: nameof(tokenType)),
-            };
+            switch (tokenType)
+            {
+                case default(TokenType):
+                    return token;
+                case TokenType.Bot:
+                    return $"Bot {token}";
+                case TokenType.Bearer:
+                    return $"Bearer {token}";
+                default:
+                    throw new ArgumentException(message: "Unknown OAuth token type.", paramName: nameof(tokenType));
+            }
         }
         internal virtual void Dispose(bool disposing)
         {
@@ -1517,7 +1521,7 @@ namespace Discord.API
         }
         private static BucketId GetBucketId(string httpMethod, BucketIds ids, Expression<Func<string>> endpointExpr, string callingMethod)
         {
-            ids.HttpMethod ??= httpMethod;
+            ids.HttpMethod = ids.HttpMethod ?? httpMethod;
             return _bucketIdGenerators.GetOrAdd(callingMethod, x => CreateBucketId(endpointExpr))(ids);
         }
 

Discord.NET/Discord.Net.WebSocket/DiscordSocketClient.cs

@@ -580,7 +580,7 @@ namespace Discord.WebSocket
                                                 return;
                                             
                                             if (BaseConfig.AlwaysDownloadUsers)
-                                                _ = DownloadUsersAsync(Guilds.Where(x => x.IsAvailable && !x.HasAllMembers));
+                                                _ = DownloadUsersAsync(Guilds.Where(x1 => x1.IsAvailable && !x1.HasAllMembers));
 
                                             await TimedInvokeAsync(_readyEvent, nameof(Ready)).ConfigureAwait(false);
                                             await _gatewayLogger.InfoAsync("Ready").ConfigureAwait(false);