Finish up by add methods to interfaces

src/Discord.Net.WebSocket/DiscordSocketConfig.cs

@@ -190,7 +190,7 @@ namespace Discord.WebSocket
         {
             WebSocketProvider = DefaultWebSocketProvider.Instance;
             UdpSocketProvider = DefaultUdpSocketProvider.Instance;
-            MessageCache = new MessageCache();
+            MessageCache = new MessageCache(MessageCacheSize);
         }
 
         internal DiscordSocketConfig Clone() => MemberwiseClone() as DiscordSocketConfig;

src/Discord.Net.WebSocket/Entities/Channels/ISocketMessageChannel.cs

@@ -17,6 +17,7 @@ namespace Discord.WebSocket
         ///     A read-only collection of WebSocket-based messages.
         /// </returns>
         IReadOnlyCollection<SocketMessage> CachedMessages { get; }
+        IMessageCache MessageCache { get; }
 
         /// <summary>
         ///     Sends a message to this message channel.

src/Discord.Net.WebSocket/Entities/Channels/SocketDMChannel.cs

@@ -25,7 +25,7 @@ namespace Discord.WebSocket
 
         /// <inheritdoc />
         public IReadOnlyCollection<SocketMessage> CachedMessages => _messages?.Messages ?? ImmutableArray.Create<SocketMessage>();
-
+        public IMessageCache MessageCache => _messages;
         /// <summary>
         ///     Gets a collection that is the current logged-in user and the recipient.
         /// </summary>
@@ -36,7 +36,7 @@ namespace Discord.WebSocket
         {
             Recipient = recipient;
             recipient.GlobalUser.AddRef();
-            _messages = discord.MessageCache.CreateMessageCache();
+            _messages = discord.MessageCache.CreateMessageCache(discord.MessageCacheSize);
         }
         internal static SocketDMChannel Create(DiscordSocketClient discord, ClientState state, Model model)
         {

src/Discord.Net.WebSocket/Entities/Channels/SocketGroupChannel.cs

@@ -31,6 +31,7 @@ namespace Discord.WebSocket
 
         /// <inheritdoc />
         public IReadOnlyCollection<SocketMessage> CachedMessages => _messages?.Messages ?? ImmutableArray.Create<SocketMessage>();
+        public IMessageCache MessageCache => _messages;
         public new IReadOnlyCollection<SocketGroupUser> Users => _users.ToReadOnlyCollection();
         public IReadOnlyCollection<SocketGroupUser> Recipients
             => _users.Select(x => x.Value).Where(x => x.Id != Discord.CurrentUser.Id).ToReadOnlyCollection(() => _users.Count - 1);
@@ -38,7 +39,7 @@ namespace Discord.WebSocket
         internal SocketGroupChannel(DiscordSocketClient discord, ulong id)
             : base(discord, id)
         {
-            _messages = discord.MessageCache.CreateMessageCache();
+            _messages = discord.MessageCache.CreateMessageCache(discord.MessageCacheSize);
             _voiceStates = new ConcurrentDictionary<ulong, SocketVoiceState>(ConcurrentHashSet.DefaultConcurrencyLevel, 5);
             _users = new ConcurrentDictionary<ulong, SocketGroupUser>(ConcurrentHashSet.DefaultConcurrencyLevel, 5);
         }

src/Discord.Net.WebSocket/Entities/Channels/SocketTextChannel.cs

@@ -44,6 +44,7 @@ namespace Discord.WebSocket
         public string Mention => MentionUtils.MentionChannel(Id);
         /// <inheritdoc />
         public IReadOnlyCollection<SocketMessage> CachedMessages => _messages?.Messages ?? ImmutableArray.Create<SocketMessage>();
+        public IMessageCache MessageCache => _messages;
         /// <inheritdoc />
         public override IReadOnlyCollection<SocketGuildUser> Users
             => Guild.Users.Where(x => Permissions.GetValue(
@@ -54,7 +55,7 @@ namespace Discord.WebSocket
             : base(discord, id, guild)
         {
             if (Discord.MessageCacheSize > 0)
-                _messages = discord.MessageCache.CreateMessageCache();
+                _messages = discord.MessageCache.CreateMessageCache(discord.MessageCacheSize);
         }
         internal new static SocketTextChannel Create(SocketGuild guild, ClientState state, Model model)
         {

src/Discord.Net.WebSocket/Entities/Messages/IMessageCache.cs

@@ -5,7 +5,7 @@ namespace Discord
 {
     public interface IMessageCache
     {
-        public IMessageCache CreateMessageCache();
+        public IMessageCache CreateMessageCache(int size);
 
         public IReadOnlyCollection<SocketMessage> Messages { get; }
 

src/Discord.Net.WebSocket/Entities/Messages/MessageCache.cs

@@ -14,11 +14,11 @@ namespace Discord.WebSocket
 
         public IReadOnlyCollection<SocketMessage> Messages => _messages.ToReadOnlyCollection();
 
-        public IMessageCache CreateMessageCache() => new MessageCache();
+        public IMessageCache CreateMessageCache(int size) => new MessageCache(size);
 
-        public MessageCache()
+        public MessageCache(int size)
         {
-            _size = 50; // todo: get this from the existing DiscordSocketConfig value.
+            _size = size;
             _messages = new ConcurrentDictionary<ulong, SocketMessage>(ConcurrentHashSet.DefaultConcurrencyLevel, (int)(_size * 1.05));
             _orderedMessages = new ConcurrentQueue<ulong>();
         }