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获取当月的第一天和最后一天示例

最简单获取当月第一天和最后一天 代码如下:

DateTime now = DateTime.Now;DateTime dt1 = new DateTime(now.Year, now.Month, 1);DateTime dt2 = d1.AddMonths(1).AddDays(-1);dt1是本月的第一天,dt2本月的最后一天,最后一天的算法是:得到本月的第一天然后增加一月,再减去一天.
智能判断每个月有多少天: 

//返回每月的第一天和最后一天 public static void ReturnDateFormat(int month, out string firstDay, out string lastDay) { int year = DateTime.Now.Year + month / 12; if (month != 12) { month = month % 12; } switch (month) { case 1,3,5,7,8,10,12: firstDay = DateTime.Now.ToString(year + "-0" + month + "-01"); lastDay = DateTime.Now.ToString(year + "-0" + month + "-31"); break;
         
case 4,6,9,11: firstDay = DateTime.Now.ToString(year + "-0" + month + "-01"); lastDay = DateTime.Now.ToString(year + "-0" + month + "-30"); break;
        
default:
            //2月
            firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");                    if (DateTime.IsLeapYear(DateTime.Now.Year))                        lastDay = DateTime.Now.ToString(year + "-0" + month + "-29");                    else                        lastDay = DateTime.Now.ToString(year + "-0" + month + "-28");                    break;
 } }

 

获取当月的第一天和最后一天示例