Improved performance where Channel.GetUser is used

src/Discord.Net/DiscordClient.cs

@@ -807,7 +807,8 @@ namespace Discord
                             Channel channel = GetChannel(data.ChannelId);
                             if (channel != null)
                             {
-                                var user = channel.GetUser(data.Author.Id);
+                                var user = channel.GetUserFast(data.Author.Id);
+
                                 if (user != null)
                                 {
                                     Message msg = null;

src/Discord.Net/Models/Channel.cs

@@ -275,7 +275,7 @@ namespace Discord
                 if (_messages.TryGetValue(id, out result))
                     return result;
             }
-            return new Message(id, this, userId != null ? GetUser(userId.Value) : null);
+            return new Message(id, this, userId != null ? GetUserFast(userId.Value) : null);
         }
 
         public async Task<Message[]> DownloadMessages(int limit = 100, ulong? relativeMessageId = null, 
@@ -298,13 +298,13 @@ namespace Discord
                     Message msg = null;
                     if (useCache)
                     {
-                        msg = AddMessage(x.Id, GetUser(x.Author.Id), x.Timestamp.Value);
+                        msg = AddMessage(x.Id, GetUserFast(x.Author.Id), x.Timestamp.Value);
                         var user = msg.User;
                         if (user != null)
                             user.UpdateActivity(msg.EditedTimestamp ?? msg.Timestamp);
                     }
                     else
-                        msg = new Message(x.Id, this, GetUser(x.Author.Id));
+                        msg = new Message(x.Id, this, GetUserFast(x.Author.Id));
                     msg.Update(x);
                     return msg;
                 })
@@ -573,6 +573,20 @@ namespace Discord
             }
             return null;
         }
+        internal User GetUserFast(ulong id)
+        {
+            //Can return users not in this channel, but that's usually okay
+            if (IsPrivate)
+            {
+                if (id == Recipient.Id)
+                    return Recipient;
+                else if (id == Client.PrivateUser.Id)
+                    return Client.PrivateUser;
+            }
+            else
+                return Server.GetUser(id);
+            return null;
+        }
         #endregion
 
         internal Channel Clone()

src/Discord.Net/Models/Message.cs

@@ -36,7 +36,7 @@ namespace Discord
                 ulong id;
                 if (e.Value.Substring(2, e.Value.Length - 3).TryToId(out id))
                 {
-                    var user = channel.GetUser(id);
+                    var user = channel.GetUserFast(id);
                     if (user != null)
                     {
                         if (users != null)
@@ -276,7 +276,7 @@ namespace Discord
 			if (model.Mentions != null)
 			{
 				MentionedUsers = model.Mentions
-					.Select(x => Channel.GetUser(x.Id))
+					.Select(x => Channel.GetUserFast(x.Id))
 					.Where(x => x != null)
 					.ToArray();
 			}