方法一：//最有含量的一种
- int days = System.Threading.Thread.CurrentThread.CurrentUICulture.Calendar.GetDaysInMonth(DateTime.Now.Year, DateTime.Now.Month);
方法二：//最奇怪的一种
- DateTime dtNow = DateTime.Today;
- int days = dtNow.AddDays(1 - dtNow.Day).AddMonths(1).AddDays(-1).Day;
方法三：//最常规的一种
- DateTime dtNow = DateTime.Now;
- int days = DateTime.DaysInMonth(dtNow.Year, dtNow.Month);