编写在C#中的消息框上单击X时的代码

using System;
using System.Windows.Forms;

namespace MessageApp
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (e.CloseReason == CloseReason.UserClosing)
            {
                DialogResult result = MessageBox.Show("确定要关闭窗口吗？", "提示", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
                if (result == DialogResult.No)
                {
                    e.Cancel = true;
                }
            }
        }
    }
}