程序退出时，显示程序运行时间

关闭程序后，显示程序运行时间。代码如下：
View Code
 1 using System;
 2 using System.Collections.Generic;
 3 using System.ComponentModel;
 4 using System.Data;
 5 using System.Drawing;
 6 using System.Linq;
 7 using System.Text;
 8 using System.Windows.Forms;
 9 using System.Diagnostics;
10 namespace time
11 {
12     public partial class Form1 : Form
13     {
14         public Form1()
15         {
16             InitializeComponent();
17         }
18         private Stopwatch stop= new Stopwatch();
19         private void Form1_Load(object sender, EventArgs e)
20         {
21             stop.Start();
22         }
23 
24         private void Form1_FormClosing(object sender, FormClosingEventArgs e)
25         {
26             DialogResult dr = MessageBox.Show("真的要退出？", "退出", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
27             if (dr == DialogResult.Yes)
28             {
29                 stop.Stop();
30                 MessageBox.Show("程序共运行时间:" + stop.Elapsed.Seconds.ToString() + "秒");
31                 e.Cancel = false;
32             }
33             else
34             {
35                 e.Cancel = true;
36             }
37         }
38     }
39 }