fixes #506 - Song list - make columns headers clickable for sorting

MediaBrowser.Controller/Entities/Audio/Audio.cs

@@ -9,7 +9,7 @@ namespace MediaBrowser.Controller.Entities.Audio
     /// <summary>
     /// Class Audio
     /// </summary>
-    public class Audio : BaseItem, IHasMediaStreams
+    public class Audio : BaseItem, IHasMediaStreams, IHasAlbumArtist
     {
         public Audio()
         {

MediaBrowser.Controller/Entities/Audio/IHasAlbumArtist.cs

@@ -0,0 +1,8 @@
+
+namespace MediaBrowser.Controller.Entities.Audio
+{
+    public interface IHasAlbumArtist
+    {
+        string AlbumArtist { get; }
+    }
+}

MediaBrowser.Controller/Entities/Audio/MusicAlbum.cs

@@ -6,7 +6,7 @@ namespace MediaBrowser.Controller.Entities.Audio
     /// <summary>
     /// Class MusicAlbum
     /// </summary>
-    public class MusicAlbum : Folder
+    public class MusicAlbum : Folder, IHasAlbumArtist
     {
         public string LastFmImageUrl { get; set; }
         
@@ -62,6 +62,17 @@ namespace MediaBrowser.Controller.Entities.Audio
         {
             return RecursiveChildren.OfType<Audio>().Any(i => i.HasArtist(artist));
         }
+
+        public string AlbumArtist
+        {
+            get
+            {
+                return RecursiveChildren
+                  .OfType<Audio>()
+                  .Select(i => i.AlbumArtist)
+                  .FirstOrDefault(i => !string.IsNullOrEmpty(i));
+            }
+        }
     }
 
     public class MusicAlbumDisc : Folder

MediaBrowser.Controller/MediaBrowser.Controller.csproj

@@ -73,6 +73,7 @@
     </Compile>
     <Compile Include="Dto\IDtoService.cs" />
     <Compile Include="Entities\AdultVideo.cs" />
+    <Compile Include="Entities\Audio\IHasAlbumArtist.cs" />
     <Compile Include="Entities\Book.cs" />
     <Compile Include="Configuration\IServerConfigurationManager.cs" />
     <Compile Include="Entities\Audio\MusicGenre.cs" />