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

src/Discord.Net.Core/Extensions/DiscordClientExtensions.cs

@@ -12,12 +12,12 @@ namespace Discord
         public static async Task<IDMChannel> GetDMChannelAsync(this IDiscordClient client, ulong id)
             => await client.GetPrivateChannelAsync(id).ConfigureAwait(false) as IDMChannel;
         public static async Task<IEnumerable<IDMChannel>> GetDMChannelsAsync(this IDiscordClient client)
-            => (await client.GetPrivateChannelsAsync().ConfigureAwait(false)).Select(x => x as IDMChannel).Where(x => x != null);
+            => (await client.GetPrivateChannelsAsync().ConfigureAwait(false)).OfType<IDMChannel>();
 
         public static async Task<IGroupChannel> GetGroupChannelAsync(this IDiscordClient client, ulong id)
             => await client.GetPrivateChannelAsync(id).ConfigureAwait(false) as IGroupChannel;
         public static async Task<IEnumerable<IGroupChannel>> GetGroupChannelsAsync(this IDiscordClient client)
-            => (await client.GetPrivateChannelsAsync().ConfigureAwait(false)).Select(x => x as IGroupChannel).Where(x => x != null);
+            => (await client.GetPrivateChannelsAsync().ConfigureAwait(false)).OfType<IGroupChannel>();
 
         public static async Task<IVoiceRegion> GetOptimalVoiceRegionAsync(this IDiscordClient discord)
         {

src/Discord.Net.Rest/Entities/Guilds/RestGuild.cs

@@ -168,7 +168,7 @@ namespace Discord.Rest
         public async Task<IReadOnlyCollection<RestTextChannel>> GetTextChannelsAsync(RequestOptions options = null)
         {
             var channels = await GuildHelper.GetChannelsAsync(this, Discord, options).ConfigureAwait(false);
-            return channels.Select(x => x as RestTextChannel).Where(x => x != null).ToImmutableArray();
+            return channels.OfType<RestTextChannel>().ToImmutableArray();
         }
         public async Task<RestVoiceChannel> GetVoiceChannelAsync(ulong id, RequestOptions options = null)
         {
@@ -178,12 +178,12 @@ namespace Discord.Rest
         public async Task<IReadOnlyCollection<RestVoiceChannel>> GetVoiceChannelsAsync(RequestOptions options = null)
         {
             var channels = await GuildHelper.GetChannelsAsync(this, Discord, options).ConfigureAwait(false);
-            return channels.Select(x => x as RestVoiceChannel).Where(x => x != null).ToImmutableArray();
+            return channels.OfType<RestVoiceChannel>().ToImmutableArray();
         }
         public async Task<IReadOnlyCollection<RestCategoryChannel>> GetCategoryChannelsAsync(RequestOptions options = null)
         {
             var channels = await GuildHelper.GetChannelsAsync(this, Discord, options).ConfigureAwait(false);
-            return channels.Select(x => x as RestCategoryChannel).Where(x => x != null).ToImmutableArray();
+            return channels.OfType<RestCategoryChannel>().ToImmutableArray();
         }
 
         public async Task<RestVoiceChannel> GetAFKChannelAsync(RequestOptions options = null)

src/Discord.Net.WebSocket/DiscordSocketClient.cs

@@ -63,9 +63,9 @@ namespace Discord.WebSocket
         public override IReadOnlyCollection<SocketGuild> Guilds => State.Guilds;
         public override IReadOnlyCollection<ISocketPrivateChannel> PrivateChannels => State.PrivateChannels;
         public IReadOnlyCollection<SocketDMChannel> DMChannels
-            => State.PrivateChannels.Select(x => x as SocketDMChannel).Where(x => x != null).ToImmutableArray();
+            => State.PrivateChannels.OfType<SocketDMChannel>().ToImmutableArray();
         public IReadOnlyCollection<SocketGroupChannel> GroupChannels
-            => State.PrivateChannels.Select(x => x as SocketGroupChannel).Where(x => x != null).ToImmutableArray();
+            => State.PrivateChannels.OfType<SocketGroupChannel>().ToImmutableArray();
         public override IReadOnlyCollection<RestVoiceRegion> VoiceRegions => _voiceRegions.ToReadOnlyCollection();
 
         /// <summary> Creates a new REST/WebSocket discord client. </summary>

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