private void Teacher_Closing(object sender, e)
        {
            DialogResult result;
            result=MessageBox.Show("确定要退出？","询问",MessageBoxButtons.YesNo);

            if(result == DialogResult.Yes)
            {

                // Closes the parent form.

                //this.Close();
            }
      }
可是当弹出对话框时，无论我点是，还是否，主窗口都会关闭~
请问一下，那个   if( result ==DialogResult.No)应该如何定义呢？谢谢！！

对哈，谢谢哈~~~~