public void Download_Click(object sender, EventArgs e) { VideoURL selectedVideoURL = this._udlView.comboBoxVideoURL.SelectedItem as VideoURL; if (selectedVideoURL == null) { throw new NullReferenceException("VideoURL is null"); } DownloadVideo downloadVideo = new DownloadVideo(selectedVideoURL, UDL.Properties.Settings.Default.OutputPath); DownloadVideoView dl = new DownloadVideoView(downloadVideo); downloadVideo.Attach(dl); dl.Show(); }