asp.net 擷取當月的第一天和最後一天樣本

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ASP.NET(C#)返回每個月的第一天和最後一天要怎麼來做呢，我們下文整理了不少例子，然後根據例子做了一個智能判斷每個月有多少天，無需你計算，本函數將替你完成： 希望對各位有協助。 

最簡單擷取當月第一天和最後一天 代碼如下

代碼如下	複製代碼
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本月的最後一天，
最後一天的演算法是：得到本月的第一天然後增加一月，再減去一天.

例子

代碼如下

複製代碼

DateTime dt = DateTime.Now;  //本月第一天時間  DateTime dt_First = dt.AddDays(-(dt.Day) + 1);  Label1.Text = dt_First.ToString("yyyy-MM-dd");  //將本月月數+1  DateTime dt2 = dt.AddMonths(1);  //本月最後一天時間  DateTime dt_Last = dt2.AddDays(-(dt.Day));  Label2.Text = dt_Last.ToString("yyyy-MM-dd");  int weeknow = Convert.ToInt32(System.DateTime.Now.DayOfWeek);  int daydiff = (-1) * weeknow + 1;  int dayadd = 7 - weeknow;

上面我們都需要手來寫，下面代碼可以實現智能判斷了

例子,智能判斷每個月有多少天，無需你計算，本函數將替你完成：

 

代碼如下

複製代碼

using System; namespace DotNet.Utilities {     public class DateFormat     {         //返回每月的第一天和最後一天         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:                     firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");                     lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");                     break;                 case 2:                     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;                 case 3:                     firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");                     lastDay = DateTime.Now.ToString("yyyy-0" + month + "-31");                     break;                 case 4:                     firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");                     lastDay = DateTime.Now.ToString(year + "-0" + month + "-30");                     break;                 case 5:                     firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");                     lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");                     break;                 case 6:                     firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");                     lastDay = DateTime.Now.ToString(year + "-0" + month + "-30");                     break;                 case 7:                     firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");                     lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");                     break;                 case 8:                     firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");                     lastDay = DateTime.Now.ToString(year + "-0" + month + "-31");                     break;                 case 9:                     firstDay = DateTime.Now.ToString(year + "-0" + month + "-01");                     lastDay = DateTime.Now.ToString(year + "-0" + month + "-30");                     break;                 case 10:                     firstDay = DateTime.Now.ToString(year + "-" + month + "-01");                     lastDay = DateTime.Now.ToString(year + "-" + month + "-31");                     break;                 case 11:                     firstDay = DateTime.Now.ToString(year + "-" + month + "-01");                     lastDay = DateTime.Now.ToString(year + "-" + month + "-30");                     break;                 default:                     firstDay = DateTime.Now.ToString(year + "-" + month + "-01");                     lastDay = DateTime.Now.ToString(year + "-" + month + "-31");                     break;             }         }     } }

asp.net 擷取當月的第一天和最後一天樣本