private void OnVideoCompleted(object sender, DownloadCompetedArgs e)
 {
     this.RaisePropertyChanged(()=>this.IsDownloaded);
     this.RaisePropertyChanged(() => this.IsDownloading);
 }
 private async void OnDownloadCompleted(object sender, DownloadCompetedArgs e)
 {
     await this.UpdateDownloadsAsync(e.Download);
 }