C# DateTime 小片段

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication4
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string str = "2009-03-20";//结束的日期
            DateTime dt2 = DateTime.Now;//获得今天的日期
            DateTime dt1 = Convert.ToDateTime(str);//把结束的日期类型转换为DateTime

            string datetime = null;//项目剩余时间

            TimeSpan st1 = new TimeSpan(dt1.Ticks);
            TimeSpan st2 = new TimeSpan(dt2.Ticks);


            TimeSpan ts = st1.Subtract(st2);//结束日期减去当前日期

            string dateTerm = ts.Days.ToString() + "天"
                      + ts.Hours.ToString() + "小时"
                      + ts.Minutes.ToString() + "分钟"
                      + ts.Seconds.ToString() + "秒";

            datetime = "离项目结束还有" + dateTerm;

            label2.Text = datetime;//显示在label里
            //MessageBox.Show(dateTerm);

        }
    }