DateTime d1 = hrStaff.DateJoin;                DateTime d2 = DateTime.Now;                TimeSpan d3 = d2.Subtract(d1);                double d4 = (double)(d3.Days) / 365;                //int interval = new TimeSpan(d2.Ticks - d1.Ticks).Days;  获取总共相差的天数                string str1 = d4.ToString("f1");//fN 保留N位，四舍五入                   //decimal dec = decimal.Round((decimal)(d3.Days) / 365, 1);   //同样能实现四舍五入保留一位小数

 参考：

http://blog.csdn.net/binzai325/article/details/6908112

http://www.cnblogs.com/sunney/archive/2010/07/28/1786903.html

http://www.zzzj.com/html/20080926/66172.html

http://www.cnblogs.com/sunney/archive/2010/07/28/1786903.html