ファイル保存ダイアログにコントロール追加(C#)

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;


using Microsoft.WindowsAPICodePack;
using Microsoft.WindowsAPICodePack.Dialogs;
using Microsoft.WindowsAPICodePack.Dialogs.Controls;
 

namespace WindowsFormsApp1
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
    }

    private void Form1_MouseClick(object sender, MouseEventArgs e)
    {

      CommonSaveFileDialog dialog = new CommonSaveFileDialog();
      CommonFileDialogCheckBox check = new CommonFileDialogCheckBox("check");
      dialog.Controls.Add(check);

      if (dialog.ShowDialog() == CommonFileDialogResult.Ok)
      {
        if (check.IsChecked == true)
        {
          MessageBox.Show("Checked");
        }
        else
        {
          MessageBox.Show("unChecked");

        }
      }

    }
  }
}