[C#] 取得本月的第一天及最後一天的日期方法

方法一：

   DateTime FirstDay = new DateTime(DateTime.Now.Year,DateTime.Now.Month,1);
   DateTime LastDay = new DateTime(DateTime.Now.AddMonths(1).Year,DateTime.Now.AddMonths(1).Month,1).AddDays(-1);

方法二：

   DateTime FirstDay = DateTime.Now.AddDays(-DateTime.Now.Day+1);
   DateTime LastDay = DateTime.Now.AddMonths(1).AddDays(-DateTime.Now.AddMonths(1).Day);