C#获取本月开始日期和结束日期

DateTime dt = DateTime.Now;
//本月第一天时间      
DateTime dt_First = dt.AddDays(1 - (dt.Day));
//获得某年某月的天数    
int year = dt.Date.Year;
int month = dt.Date.Month;
int dayCount = DateTime.DaysInMonth(year, month);
//本月最后一天时间    
DateTime dt_Last = dt_First.AddDays(dayCount - 1);
dtpDateTime.Value = dt_First;
dtpEndTime.Value = dt_Last;