var ms = new MemoryStream();
await Browser.CoreWebView2.CapturePreviewAsync(CoreWebView2CapturePreviewImageFormat.Png, ms);
    var bytes = ms.ToArray();
    var dlg = new System.Windows.Forms.SaveFileDialog();
    dlg.Title = "保存截图";
    dlg.FileName = M3u8DownloadTask.GetValidFileName(title ?? "网页截图") + ".png";
    dlg.Filter = "PNG图片 (*.PNG)|*.PNG";
    if (dlg.ShowDialog() != DialogResult.OK)
        return;
    var file = dlg.FileName;
    File.WriteAllBytes(file, bytes);