Fixed crash, added DM/Group channel helpers

src/Discord.Net.Core/IDiscordClient.cs

@@ -17,6 +17,8 @@ namespace Discord
 
         Task<IChannel> GetChannelAsync(ulong id, CacheMode mode = CacheMode.AllowDownload);
         Task<IReadOnlyCollection<IPrivateChannel>> GetPrivateChannelsAsync(CacheMode mode = CacheMode.AllowDownload);
+        Task<IReadOnlyCollection<IDMChannel>> GetDMChannelsAsync(CacheMode mode = CacheMode.AllowDownload);
+        Task<IReadOnlyCollection<IGroupChannel>> GetGroupChannelsAsync(CacheMode mode = CacheMode.AllowDownload);
 
         Task<IReadOnlyCollection<IConnection>> GetConnectionsAsync();
 

src/Discord.Net.Rest/BaseDiscordClient.cs

@@ -134,6 +134,10 @@ namespace Discord.Rest
             => Task.FromResult<IChannel>(null);
         Task<IReadOnlyCollection<IPrivateChannel>> IDiscordClient.GetPrivateChannelsAsync(CacheMode mode)
             => Task.FromResult<IReadOnlyCollection<IPrivateChannel>>(ImmutableArray.Create<IPrivateChannel>());
+        Task<IReadOnlyCollection<IDMChannel>> IDiscordClient.GetDMChannelsAsync(CacheMode mode)
+            => Task.FromResult<IReadOnlyCollection<IDMChannel>>(ImmutableArray.Create<IDMChannel>());
+        Task<IReadOnlyCollection<IGroupChannel>> IDiscordClient.GetGroupChannelsAsync(CacheMode mode)
+            => Task.FromResult<IReadOnlyCollection<IGroupChannel>>(ImmutableArray.Create<IGroupChannel>());
 
         Task<IReadOnlyCollection<IConnection>> IDiscordClient.GetConnectionsAsync()
             => Task.FromResult<IReadOnlyCollection<IConnection>>(ImmutableArray.Create<IConnection>());

src/Discord.Net.Rest/ClientHelper.cs

@@ -24,10 +24,24 @@ namespace Discord.Rest
                 return RestChannel.Create(client, model);
             return null;
         }
-        public static async Task<IReadOnlyCollection<IPrivateChannel>> GetPrivateChannelsAsync(BaseDiscordClient client)
+        public static async Task<IReadOnlyCollection<IRestPrivateChannel>> GetPrivateChannelsAsync(BaseDiscordClient client)
         {
             var models = await client.ApiClient.GetMyPrivateChannelsAsync().ConfigureAwait(false);
-            return models.Select(x => RestDMChannel.Create(client, x)).ToImmutableArray();
+            return models.Select(x => RestChannel.CreatePrivate(client, x)).ToImmutableArray();
+        }
+        public static async Task<IReadOnlyCollection<RestDMChannel>> GetDMChannelsAsync(BaseDiscordClient client)
+        {
+            var models = await client.ApiClient.GetMyPrivateChannelsAsync().ConfigureAwait(false);
+            return models
+                .Where(x => x.Type == ChannelType.DM)
+                .Select(x => RestDMChannel.Create(client, x)).ToImmutableArray();
+        }
+        public static async Task<IReadOnlyCollection<RestGroupChannel>> GetGroupChannelsAsync(BaseDiscordClient client)
+        {
+            var models = await client.ApiClient.GetMyPrivateChannelsAsync().ConfigureAwait(false);
+            return models
+                .Where(x => x.Type == ChannelType.Group)
+                .Select(x => RestGroupChannel.Create(client, x)).ToImmutableArray();
         }
         
         public static async Task<IReadOnlyCollection<RestConnection>> GetConnectionsAsync(BaseDiscordClient client)

src/Discord.Net.Rest/DiscordRestClient.cs

@@ -39,8 +39,12 @@ namespace Discord.Rest
         public Task<RestChannel> GetChannelAsync(ulong id)
             => ClientHelper.GetChannelAsync(this, id);
         /// <inheritdoc />
-        public Task<IReadOnlyCollection<IPrivateChannel>> GetPrivateChannelsAsync()
+        public Task<IReadOnlyCollection<IRestPrivateChannel>> GetPrivateChannelsAsync()
             => ClientHelper.GetPrivateChannelsAsync(this);
+        public Task<IReadOnlyCollection<RestDMChannel>> GetDMChannelsAsync()
+            => ClientHelper.GetDMChannelsAsync(this);
+        public Task<IReadOnlyCollection<RestGroupChannel>> GetGroupChannelsAsync()
+            => ClientHelper.GetGroupChannelsAsync(this);
 
         /// <inheritdoc />
         public Task<IReadOnlyCollection<RestConnection>> GetConnectionsAsync()
@@ -98,6 +102,20 @@ namespace Discord.Rest
             else
                 return ImmutableArray.Create<IPrivateChannel>();
         }
+        async Task<IReadOnlyCollection<IDMChannel>> IDiscordClient.GetDMChannelsAsync(CacheMode mode)
+        {
+            if (mode == CacheMode.AllowDownload)
+                return await GetDMChannelsAsync().ConfigureAwait(false);
+            else
+                return ImmutableArray.Create<IDMChannel>();
+        }
+        async Task<IReadOnlyCollection<IGroupChannel>> IDiscordClient.GetGroupChannelsAsync(CacheMode mode)
+        {
+            if (mode == CacheMode.AllowDownload)
+                return await GetGroupChannelsAsync().ConfigureAwait(false);
+            else
+                return ImmutableArray.Create<IGroupChannel>();
+        }
 
         async Task<IReadOnlyCollection<IConnection>> IDiscordClient.GetConnectionsAsync()
             => await GetConnectionsAsync().ConfigureAwait(false);

src/Discord.Net.WebSocket/DiscordSocketClient.cs

@@ -68,6 +68,10 @@ namespace Discord.WebSocket
         public new SocketSelfUser CurrentUser { get { return base.CurrentUser as SocketSelfUser; } private set { base.CurrentUser = value; } }
         public IReadOnlyCollection<SocketGuild> Guilds => State.Guilds;
         public IReadOnlyCollection<ISocketPrivateChannel> PrivateChannels => State.PrivateChannels;
+        public IReadOnlyCollection<SocketDMChannel> DMChannels 
+            => State.PrivateChannels.Select(x => x as SocketDMChannel).Where(x => x != null).ToImmutableArray();
+        public IReadOnlyCollection<SocketGroupChannel> GroupChannels 
+            => State.PrivateChannels.Select(x => x as SocketGroupChannel).Where(x => x != null).ToImmutableArray();
         public IReadOnlyCollection<RestVoiceRegion> VoiceRegions => _voiceRegions.ToReadOnlyCollection();
 
         /// <summary> Creates a new REST/WebSocket discord client. </summary>
@@ -1803,6 +1807,10 @@ namespace Discord.WebSocket
             => Task.FromResult<IChannel>(GetChannel(id));
         Task<IReadOnlyCollection<IPrivateChannel>> IDiscordClient.GetPrivateChannelsAsync(CacheMode mode)
             => Task.FromResult<IReadOnlyCollection<IPrivateChannel>>(PrivateChannels);
+        Task<IReadOnlyCollection<IDMChannel>> IDiscordClient.GetDMChannelsAsync(CacheMode mode)
+            => Task.FromResult<IReadOnlyCollection<IDMChannel>>(DMChannels);
+        Task<IReadOnlyCollection<IGroupChannel>> IDiscordClient.GetGroupChannelsAsync(CacheMode mode)
+            => Task.FromResult<IReadOnlyCollection<IGroupChannel>>(GroupChannels);
 
         async Task<IReadOnlyCollection<IConnection>> IDiscordClient.GetConnectionsAsync()
             => await GetConnectionsAsync().ConfigureAwait(false);