public override async Task Download()
 {
     try
     {
         var item = Info.Entity as SongViewModel;
         if (item == null)
         {
             throw new Exception("song item is null");
         }
         if (string.IsNullOrEmpty(item.UrlLrc))
         {
             item.UrlLrc = await NetAccess.GetUrlLrc(item.Id);
         }
         Info.Url = item.UrlLrc;
         if (string.IsNullOrEmpty(Info.Url))
         {
             State = EnumDownloadState.Error;
             NotifyState();
             return;
         }
     }
     catch (Exception e)
     {
         NotifyError(e);
         return;
     }
     await base.Download();
 }