c# 实现子窗口关闭父窗口也关闭的方法

public delegate void childclose();
public event childclose closefather;

private void Form2_Closed(object sender, System.EventArgs e)
   {
    //用事件去关闭主窗口
    closefather();
   }

Form2 ff=new Form2();
ff.closefather+=new childclose(this.closethis); //closethis()是父窗体中的一个方法
  ff.Show();

   public void closethis()
   {
     this.Close();
   }