將DateTime設置爲月份開始

Question

如何在C＃中將DateTime設置爲月份的第一個月？

Answer 1

var now = DateTime.Now; 
var startOfMonth = new DateTime(now.Year,now.Month,1); 

Answer 2

DateTime now = DateTime.Now; 
DateTime date = new DateTime(now.Year, now.Month, 1); 

您可以用別的代替DateTime.Now

Answer 3

像這樣的工作

DateTime firstDay = DateTime.Today.AddDays(1 - DateTime.Today.Day); 

Answer 4

這應該是高效的和正確的：

DateTime RoundDateTimeToMonth(DateTime time) 
{ 
    long ticks = time.Ticks; 
    return new DateTime((ticks/TimeSpan.TicksPerDay - time.Day + 1) * TimeSpan.TicksPerDay, time.Kind); 
} 

這裏ticks/TimeSpan.TicksPerDay re將達到給定的time和- time.Day + 1的整數天數重置爲月初。

Answer 5

有點遲到了，但這裏是沒有的伎倆，我

public static class DateTimeExtensions 
{ 
    public static DateTime FirstDayOfMonth(this DateTime dt) 
    { 
    return new DateTime(dt.Year, dt.Month, 1); 
    } 
} 

Answer 6

public static DateTime FirstDayOfMonth(this DateTime current) 
{ 
    return current.AddDays(1 - current.Day); 
} 

Answer 7

擴展方法我剛剛創建基於尼克的答案和一些擴展方法人對SO

public static class DateTimeExtensions 
    { 
     /// <summary> 
     /// get the datetime of the start of the week 
     /// </summary> 
     /// <param name="dt"></param> 
     /// <param name="startOfWeek"></param> 
     /// <returns></returns> 
     /// <example> 
     /// DateTime dt = DateTime.Now.StartOfWeek(DayOfWeek.Monday); 
     /// DateTime dt = DateTime.Now.StartOfWeek(DayOfWeek.Sunday); 
     /// </example> 
     /// <remarks>http://stackoverflow.com/a/38064/428061</remarks> 
     public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek) 
     { 
      var diff = dt.DayOfWeek - startOfWeek; 
      if (diff < 0) 
       diff += 7; 

      return dt.AddDays(-1 * diff).Date; 
     } 

     /// <summary> 
     /// get the datetime of the start of the month 
     /// </summary> 
     /// <param name="dt"></param> 
     /// <returns></returns> 
     /// <remarks>http://stackoverflow.com/a/5002582/428061</remarks> 
     public static DateTime StartOfMonth(this DateTime dt) 
     { 
      var now = DateTime.Now; 
      return new DateTime(now.Year, now.Month, 1); 
     } 

     /// <summary> 
     /// get datetime of the start of the year 
     /// </summary> 
     /// <param name="dt"></param> 
     /// <returns></returns> 
     public static DateTime StartOfYear(this DateTime dt) 
     { 
      var now = DateTime.Now; 
      return new DateTime(now.Year, 1, 1); 
     } 
    } 

Answer 8

var currentDate = DateTime.UtcNow.Date; 
var startDateTimeOfCurrentMonth = currentDate.AddDays(-(currentDate.Day - 1)); 

Answer 9

希望這有助於你。

textbox1.Text =「01-」+ DateTime.Now.ToString（「MMM-yyyy」）;