formclosing的写法

private void main_FormClosing(object sender, FormClosingEventArgs e)        {            DialogResult dr = MessageBox.Show(this, "你确定要退出吗？", "退出系统通知", MessageBoxButtons.YesNo, MessageBoxIcon.Question);            if (dr != DialogResult.Yes)            {                e.Cancel = true;

            }            else            {                Application.ExitThread();                Application.Exit();

            }