对话框中CalendarDatePicker的阴影

Question

CalendarDatePicker弹出按钮上有阴影。该“效果”可能连接到承载控件的对话框。我附加了Dialog的功能。你知道如何删除它吗？

图片：https://ibb.co/ZJjqfWs

private async void CreateNewDocumentDialog() {
    // Creating dialoge window
    var textBlock1 = new TextBlock
    {
        Text = "Kérem adja meg az alábbi adatokat!",
        FontSize = 16
    };
    var docName = new TextBox
    {
        Name = "docName",
        Margin = new Thickness(0, 10, 0, 10),
        PlaceholderText = "Documentum neve"
    };
    var docValidUntil = new CalendarDatePicker
    {
        Header = "Dokumentum érvényessége:",
        Date = DateTime.Now.AddYears(4),
    };
    var contentPanel = new StackPanel();
    contentPanel.Children.Add(textBlock1);
    contentPanel.Children.Add(docName);
    contentPanel.Children.Add(docValidUntil);
    ContentDialog CreateNewDocumentDialog = new ContentDialog
    {
        Content = contentPanel,
        PrimaryButtonText = "Új bejegyzés létrehozása",
        CloseButtonText = "Mégse",
        // Default button responds to Enter
        DefaultButton = ContentDialogButton.Primary
    };

    // Waiting for user input
    ContentDialogResult result = await CreateNewDocumentDialog.ShowAsync();

    if (result == ContentDialogResult.Primary)
    {
        // Process user input if Create New button pressed/activated
        if (docName.Text != "")
        {
            var tempDate = docValidUntil.Date;
            DocumentList.Add(new Document(docName.Text,  tempDate.Value.DateTime));
        }
    }
    else
    {
        // Exit dialog if Cancel button pressed
    }
}