mono touch中UIAlertView对话框多选项处理

//"取消"=>0, "标清"=>1, "高清"=>2UIAlertView alert = new UIAlertView ("提示", "请选择视频版本", null, "取消", new string[] { "标清", "高清" });alert.Clicked += (s, b) => {if (b.ButtonIndex != 0) {string _url = b.ButtonIndex == 1 ?              TableItems [indexPath.Row].DOWNLOAD_URL_LOW :              TableItems [indexPath.Row].DOWNLOAD_URL;string _cp = FileHelper.GetMyDocumentPath (KeyCenter.Key_CoursePath);//课程路径string _sub = TableItems [indexPath.Row].Course_Number;string _name = StringHelper.GetUrlFileName (_url);int tag = 1; //检查是否下载过了if (FileHelper.FileUploaded (_cp + _sub, _name)) {tag = 2;}base.RowTouch2View = new CourseCenter (TableItems [indexPath.Row], tag, 2);base.RowSelected (tableView, indexPath);}tableView.DeselectRow (indexPath, true);};alert.Show ();