public KCategory[] GetCategories()
 {
     var source = new KhanDataSource();
     return source.Categories.Select(c => new KCategory
         {
             Description = c.Description,
             ID = c.ID,
             Name = c.Name
         }).ToArray();
 }
 public KVideo[] GetVideos(string category)
 {
     var source = new KhanDataSource();
     return source.Videos
         .Where(v => v.Category == category)
         .Select(v => new KVideo
             {
                 Category = v.Category,
                 Description = v.Description,
                 ID = v.ID,
                 Name = v.Name,
                 Uri = v.Uri
             })
         .ToArray();
 }