C#：求两个日期之间的天数

1.

DateTime t1 = Convert.ToDateTime("1999-8-9");
DateTime t2 = Convert.ToDateTime("2007-8-19");
TimeSpan ts = t2 - t1;
int d = ts.Days;
d就是间隔的天数

 2.

TimeSpan   ts=System.DateTime.Now   -   Convert.ToDateTime("2004-09-01");  
  int   days=   ts.TotalDays;     
  事件相减，结果是一个TimeSpan类

3.

DateTime TwoDate = Convert.ToDateTime(textBox1.Text);
TimeSpan ts = DateTime.Now.Subtract(TwoDate);
int days = ts.Days;
textBox2.Text = ts.ToString();