Add various optimizations and cleanups (#1114)

* Change all Select(... as ...) to OfType

* Add changes according to 194a8aa427

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

@@ -97,7 +97,7 @@ namespace Discord.WebSocket
             if (id == Recipient.Id)
                 return Recipient;
             else if (id == Discord.CurrentUser.Id)
-                return Discord.CurrentUser as SocketSelfUser;
+                return Discord.CurrentUser;
             else
                 return null;
         }

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

@@ -18,10 +18,10 @@ namespace Discord.WebSocket
     public class SocketGroupChannel : SocketChannel, IGroupChannel, ISocketPrivateChannel, ISocketMessageChannel, ISocketAudioChannel
     {
         private readonly MessageCache _messages;
+        private readonly ConcurrentDictionary<ulong, SocketVoiceState> _voiceStates;
 
         private string _iconId;
         private ConcurrentDictionary<ulong, SocketGroupUser> _users;
-        private ConcurrentDictionary<ulong, SocketVoiceState> _voiceStates;
 
         public string Name { get; private set; }
 
@@ -129,7 +129,7 @@ namespace Discord.WebSocket
         internal SocketGroupUser GetOrAddUser(UserModel model)
         {
             if (_users.TryGetValue(model.Id, out SocketGroupUser user))
-                return user as SocketGroupUser;
+                return user;
             else
             {
                 var privateUser = SocketGroupUser.Create(this, Discord.State, model);
@@ -143,7 +143,7 @@ namespace Discord.WebSocket
             if (_users.TryRemove(id, out SocketGroupUser user))
             {
                 user.GlobalUser.RemoveRef(Discord);
-                return user as SocketGroupUser;
+                return user;
             }
             return null;
         }

src/Discord.Net.WebSocket/Entities/Guilds/SocketGuild.cs

@@ -91,11 +91,11 @@ namespace Discord.WebSocket
             }
         }
         public IReadOnlyCollection<SocketTextChannel> TextChannels
-            => Channels.Select(x => x as SocketTextChannel).Where(x => x != null).ToImmutableArray();
+            => Channels.OfType<SocketTextChannel>().ToImmutableArray();
         public IReadOnlyCollection<SocketVoiceChannel> VoiceChannels
-            => Channels.Select(x => x as SocketVoiceChannel).Where(x => x != null).ToImmutableArray();
+            => Channels.OfType<SocketVoiceChannel>().ToImmutableArray();
         public IReadOnlyCollection<SocketCategoryChannel> CategoryChannels
-            => Channels.Select(x => x as SocketCategoryChannel).Where(x => x != null).ToImmutableArray();
+            => Channels.OfType<SocketCategoryChannel>().ToImmutableArray();
         public SocketGuildUser CurrentUser => _members.TryGetValue(Discord.CurrentUser.Id, out SocketGuildUser member) ? member : null;
         public SocketRole EveryoneRole => GetRole(Id);
         public IReadOnlyCollection<SocketGuildChannel> Channels
@@ -563,7 +563,7 @@ namespace Discord.WebSocket
 
                 await Discord.ApiClient.SendVoiceStateUpdateAsync(Id, channelId, selfDeaf, selfMute).ConfigureAwait(false);
             }
-            catch (Exception)
+            catch
             {
                 await DisconnectAudioInternalAsync().ConfigureAwait(false);
                 throw;
@@ -580,7 +580,7 @@ namespace Discord.WebSocket
                     throw new TimeoutException();
                 return await promise.Task.ConfigureAwait(false);
             }
-            catch (Exception)
+            catch
             {
                 await DisconnectAudioAsync().ConfigureAwait(false);
                 throw;

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

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -28,7 +28,7 @@ namespace Discord.WebSocket
                 _orderedMessages.Enqueue(message.Id);
 
                 while (_orderedMessages.Count > _size && _orderedMessages.TryDequeue(out ulong msgId))
-                    _messages.TryRemove(msgId, out SocketMessage msg);
+                    _messages.TryRemove(msgId, out _);
             }
         }
 

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

@@ -12,12 +12,12 @@ namespace Discord.WebSocket
     [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
     public class SocketUserMessage : SocketMessage, IUserMessage
     {
+        private readonly List<SocketReaction> _reactions = new List<SocketReaction>();
         private bool _isMentioningEveryone, _isTTS, _isPinned;
         private long? _editedTimestampTicks;
         private ImmutableArray<Attachment> _attachments;
         private ImmutableArray<Embed> _embeds;
         private ImmutableArray<ITag> _tags;
-        private List<SocketReaction> _reactions = new List<SocketReaction>();
         
         public override bool IsTTS => _isTTS;
         public override bool IsPinned => _isPinned;