如何知道一周的开始(周日和周一)只知道C#中的当前时间?
类似的东西:
DateTime.Now.StartWeek(Monday);
答案 0 :(得分:656)
使用扩展方法。你知道,他们是一切的答案! ;)
public static class DateTimeExtensions
{
public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
{
int diff = (7 + (dt.DayOfWeek - startOfWeek)) % 7;
return dt.AddDays(-1 * diff).Date;
}
}
可以使用如下:
DateTime dt = DateTime.Now.StartOfWeek(DayOfWeek.Monday);
DateTime dt = DateTime.Now.StartOfWeek(DayOfWeek.Sunday);
答案 1 :(得分:65)
我能想出的最快方式是:
var sunday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek);
如果您希望将一周中的任何其他日期作为开始日期,您只需将DayOfWeek值添加到结尾
var monday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek + (int)DayOfWeek.Monday);
var tuesday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek + (int)DayOfWeek.Tuesday);
答案 2 :(得分:62)
更加冗长和文化意识:
System.Globalization.CultureInfo ci =
System.Threading.Thread.CurrentThread.CurrentCulture;
DayOfWeek fdow = ci.DateTimeFormat.FirstDayOfWeek;
DayOfWeek today = DateTime.Now.DayOfWeek;
DateTime sow = DateTime.Now.AddDays(-(today - fdow)).Date;
答案 3 :(得分:36)
var monday = DateTime.Now.Previous(DayOfWeek.Monday);
var sunday = DateTime.Now.Previous(DayOfWeek.Sunday);
答案 4 :(得分:17)
丑陋但它至少给出了正确的约会
由系统设置的星期开始:
public static DateTime FirstDateInWeek(this DateTime dt)
{
while (dt.DayOfWeek != System.Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat.FirstDayOfWeek)
dt = dt.AddDays(-1);
return dt;
}
不
public static DateTime FirstDateInWeek(this DateTime dt, DayOfWeek weekStartDay)
{
while (dt.DayOfWeek != weekStartDay)
dt = dt.AddDays(-1);
return dt;
}
答案 5 :(得分:14)
让我们结合文化安全答案和扩展方法答案:
public static class DateTimeExtensions
{
public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
{
System.Globalization.CultureInfo ci = System.Threading.Thread.CurrentThread.CurrentCulture;
DayOfWeek fdow = ci.DateTimeFormat.FirstDayOfWeek;
return DateTime.Today.AddDays(-(DateTime.Today.DayOfWeek- fdow));
}
}
答案 6 :(得分:9)
这可能有点乱,但你可以将.DayOfWeek属性转换为int(它是一个枚举,因为它没有更改它的底层数据类型,它默认为int)并使用它来确定上一个开始本周。
看起来DayOfWeek枚举中指定的星期在星期日开始,所以如果我们从这个值中减去1,那么它将等于星期一在当前日期之前的天数。我们还需要将星期日(0)映射到等于7,因此给定1 - 7 = -6星期日将映射到上一个星期一: -
DateTime now = DateTime.Now;
int dayOfWeek = (int)now.DayOfWeek;
dayOfWeek = dayOfWeek == 0 ? 7 : dayOfWeek;
DateTime startOfWeek = now.AddDays(1 - (int)now.DayOfWeek);
上周日的代码更简单,因为我们无需进行此调整: -
DateTime now = DateTime.Now;
int dayOfWeek = (int)now.DayOfWeek;
DateTime startOfWeek = now.AddDays(-(int)now.DayOfWeek);
答案 7 :(得分:8)
这会给你前一个星期天(我想):
DateTime t = DateTime.Now;
t -= new TimeSpan ((int) t.DayOfWeek, 0, 0, 0);
答案 8 :(得分:6)
周一
DateTime startAtMonday = DateTime.Now.AddDays(DayOfWeek.Monday - DateTime.Now.DayOfWeek);
在星期日
DateTime startAtSunday = DateTime.Now.AddDays(DayOfWeek.Sunday- DateTime.Now.DayOfWeek);
答案 9 :(得分:5)
using System;
using System.Globalization;
namespace MySpace
{
public static class DateTimeExtention
{
// ToDo: Need to provide culturaly neutral versions.
public static DateTime GetStartOfWeek(this DateTime dt)
{
DateTime ndt = dt.Subtract(TimeSpan.FromDays((int)dt.DayOfWeek));
return new DateTime(ndt.Year, ndt.Month, ndt.Day, 0, 0, 0, 0);
}
public static DateTime GetEndOfWeek(this DateTime dt)
{
DateTime ndt = dt.GetStartOfWeek().AddDays(6);
return new DateTime(ndt.Year, ndt.Month, ndt.Day, 23, 59, 59, 999);
}
public static DateTime GetStartOfWeek(this DateTime dt, int year, int week)
{
DateTime dayInWeek = new DateTime(year, 1, 1).AddDays((week - 1) * 7);
return dayInWeek.GetStartOfWeek();
}
public static DateTime GetEndOfWeek(this DateTime dt, int year, int week)
{
DateTime dayInWeek = new DateTime(year, 1, 1).AddDays((week - 1) * 7);
return dayInWeek.GetEndOfWeek();
}
}
}
答案 10 :(得分:3)
全部化,并允许指定一周的第一天作为通话的一部分
public static DateTime StartOfWeek ( this DateTime dt, DayOfWeek? firstDayOfWeek )
{
DayOfWeek fdow;
if ( firstDayOfWeek.HasValue )
{
fdow = firstDayOfWeek.Value;
}
else
{
System.Globalization.CultureInfo ci = System.Threading.Thread.CurrentThread.CurrentCulture;
fdow = ci.DateTimeFormat.FirstDayOfWeek;
}
int diff = dt.DayOfWeek - fdow;
if ( diff < 0 )
{
diff += 7;
}
return dt.AddDays( -1 * diff ).Date;
}
答案 11 :(得分:3)
var now = System.DateTime.Now;
var result = now.AddDays(-((now.DayOfWeek - System.Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat.FirstDayOfWeek + 7) % 7)).Date;
答案 12 :(得分:2)
尝试过几次,但没有在星期一开始的一周内解决问题,导致我在周日给我一个星期一。所以我修改了一下并使用了这段代码:
int delta = DayOfWeek.Monday - DateTime.Now.DayOfWeek;
DateTime monday = DateTime.Now.AddDays(delta == 1 ? -6 : delta);
return monday;
答案 13 :(得分:2)
在c#中尝试这个。使用此代码,您可以获得给定周的第一个日期和最后日期。这周是第一天,周六是最后一天,但您可以根据您的文化设置两个日期
DateTime firstDate = GetFirstDateOfWeek(DateTime.Parse("05/09/2012").Date,DayOfWeek.Sunday);
DateTime lastDate = GetLastDateOfWeek(DateTime.Parse("05/09/2012").Date, DayOfWeek.Saturday);
public static DateTime GetFirstDateOfWeek(DateTime dayInWeek, DayOfWeek firstDay)
{
DateTime firstDayInWeek = dayInWeek.Date;
while (firstDayInWeek.DayOfWeek != firstDay)
firstDayInWeek = firstDayInWeek.AddDays(-1);
return firstDayInWeek;
}
public static DateTime GetLastDateOfWeek(DateTime dayInWeek, DayOfWeek firstDay)
{
DateTime lastDayInWeek = dayInWeek.Date;
while (lastDayInWeek.DayOfWeek != firstDay)
lastDayInWeek = lastDayInWeek.AddDays(1);
return lastDayInWeek;
}
答案 14 :(得分:2)
这会让你在一周的第一个星期天午夜:
DateTime t = DateTime.Now;
t -= new TimeSpan ((int) t.DayOfWeek, t.Hour, t.Minute, t.Second);
这会让你在午夜的第一个星期一:
DateTime t = DateTime.Now;
t -= new TimeSpan ((int) t.DayOfWeek - 1, t.Hour, t.Minute, t.Second);
答案 15 :(得分:1)
以下方法应返回所需的DateTime。传递给星期日是星期一的第一天,星期一是假的:
private DateTime getStartOfWeek(bool useSunday)
{
DateTime now = DateTime.Now;
int dayOfWeek = (int)now.DayOfWeek;
if(!useSunday)
dayOfWeek--;
if(dayOfWeek < 0)
{// day of week is Sunday and we want to use Monday as the start of the week
// Sunday is now the seventh day of the week
dayOfWeek = 6;
}
return now.AddDays(-1 * (double)dayOfWeek);
}
答案 16 :(得分:1)
相同的一周(以@Compile的风格这个答案):
public static DateTime EndOfWeek(this DateTime dt)
{
int diff = 7 - (int)dt.DayOfWeek;
diff = diff == 7 ? 0 : diff;
DateTime eow = dt.AddDays(diff).Date;
return new DateTime(eow.Year, eow.Month, eow.Day, 23, 59, 59, 999) { };
}
答案 17 :(得分:1)
步骤1: 创建一个静态类
public static class TIMEE
{
public static DateTime StartOfWeek(this DateTime dt, DayOfWeek startOfWeek)
{
int diff = (7 + (dt.DayOfWeek - startOfWeek)) % 7;
return dt.AddDays(-1 * diff).Date;
}
public static DateTime EndOfWeek(this DateTime dt, DayOfWeek startOfWeek)
{
int diff = (7 - (dt.DayOfWeek - startOfWeek)) % 7;
return dt.AddDays(1 * diff).Date;
}
}
Step2:使用此类可获取一周的开始和结束日期
DateTime dt =TIMEE.StartOfWeek(DateTime.Now ,DayOfWeek.Monday);
DateTime dt1 = TIMEE.EndOfWeek(DateTime.Now, DayOfWeek.Sunday);
答案 18 :(得分:1)
C#中的模数对于-1mod7不好(应该是6,c#返回-1) 所以...“oneliner”对此的解决方案将如下所示:)
private static DateTime GetFirstDayOfWeek(DateTime date)
{
return date.AddDays(-(((int)date.DayOfWeek - 1) - (int)Math.Floor((double)((int)date.DayOfWeek - 1) / 7) * 7));
}
答案 19 :(得分:1)
似乎没有人正确回答这个问题。我会在这里粘贴我的解决方案,以防任何人需要它。无论一周的第一天是星期一还是星期日或其他什么,以下代码都有效。
public static class DateTimeExtension
{
public static DateTime GetFirstDayOfThisWeek(this DateTime d)
{
CultureInfo ci = System.Threading.Thread.CurrentThread.CurrentCulture;
var first = (int)ci.DateTimeFormat.FirstDayOfWeek;
var current = (int)d.DayOfWeek;
var result = first <= current ?
d.AddDays(-1 * (current - first)) :
d.AddDays(first - current - 7);
return result;
}
}
class Program
{
static void Main()
{
System.Threading.Thread.CurrentThread.CurrentCulture = CultureInfo.GetCultureInfo("en-US");
Console.WriteLine("Current culture set to en-US");
RunTests();
Console.WriteLine();
System.Threading.Thread.CurrentThread.CurrentCulture = CultureInfo.GetCultureInfo("da-DK");
Console.WriteLine("Current culture set to da-DK");
RunTests();
Console.ReadLine();
}
static void RunTests()
{
Console.WriteLine("Today {1}: {0}", DateTime.Today.Date.GetFirstDayOfThisWeek(), DateTime.Today.Date.ToString("yyyy-MM-dd"));
Console.WriteLine("Saturday 2013-03-02: {0}", new DateTime(2013, 3, 2).GetFirstDayOfThisWeek());
Console.WriteLine("Sunday 2013-03-03: {0}", new DateTime(2013, 3, 3).GetFirstDayOfThisWeek());
Console.WriteLine("Monday 2013-03-04: {0}", new DateTime(2013, 3, 4).GetFirstDayOfThisWeek());
}
}
答案 20 :(得分:1)
感谢您的示例。我需要总是使用“CurrentCulture”一周的第一天和数组我需要知道确切的Daynumber ..所以这是我的第一个扩展:
public static class DateTimeExtensions
{
//http://stackoverflow.com/questions/38039/how-can-i-get-the-datetime-for-the-start-of-the-week
//http://stackoverflow.com/questions/1788508/calculate-date-with-monday-as-dayofweek1
public static DateTime StartOfWeek(this DateTime dt)
{
//difference in days
int diff = (int)dt.DayOfWeek - (int)CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek; //sunday=always0, monday=always1, etc.
//As a result we need to have day 0,1,2,3,4,5,6
if (diff < 0)
{
diff += 7;
}
return dt.AddDays(-1 * diff).Date;
}
public static int DayNoOfWeek(this DateTime dt)
{
//difference in days
int diff = (int)dt.DayOfWeek - (int)CultureInfo.CurrentCulture.DateTimeFormat.FirstDayOfWeek; //sunday=always0, monday=always1, etc.
//As a result we need to have day 0,1,2,3,4,5,6
if (diff < 0)
{
diff += 7;
}
return diff + 1; //Make it 1..7
}
}
答案 21 :(得分:0)
namespace DateTimeExample
{
using System;
public static class DateTimeExtension
{
public static DateTime GetMonday(this DateTime time)
{
if (time.DayOfWeek != DayOfWeek.Monday)
return GetMonday(time.AddDays(-1)); //Recursive call
return time;
}
}
internal class Program
{
private static void Main()
{
Console.WriteLine(DateTime.Now.GetMonday());
Console.ReadLine();
}
}
}
答案 22 :(得分:0)
这将返回一周的开头和周末的日期:
private string[] GetWeekRange(DateTime dateToCheck)
{
string[] result = new string[2];
TimeSpan duration = new TimeSpan(0, 0, 0, 0); //One day
DateTime dateRangeBegin = dateToCheck;
DateTime dateRangeEnd = DateTime.Today.Add(duration);
dateRangeBegin = dateToCheck.AddDays(-(int)dateToCheck.DayOfWeek);
dateRangeEnd = dateToCheck.AddDays(6 - (int)dateToCheck.DayOfWeek);
result[0] = dateRangeBegin.Date.ToString();
result[1] = dateRangeEnd.Date.ToString();
return result;
}
我已在博客上发布了用于计算周,月,季度和年度开始/结束的完整代码 ZamirsBlog
答案 23 :(得分:0)
以下是一些答案的组合。它使用一种扩展方法,允许传入文化,如果没有传入,则使用当前文化。这将为其提供最大的灵活性和重复使用。
/// <summary>
/// Gets the date of the first day of the week for the date.
/// </summary>
/// <param name="date">The date to be used</param>
/// <param name="cultureInfo">If none is provided, the current culture is used</param>
/// <returns>The date of the beggining of the week based on the culture specifed</returns>
public static DateTime StartOfWeek(this DateTime date, CultureInfo cultureInfo=null) =>
date.AddDays(-1 * (7 + (date.DayOfWeek - (cultureInfo??CultureInfo.CurrentCulture).DateTimeFormat.FirstDayOfWeek)) % 7).Date;
示例用法:
public static void TestFirstDayOfWeekExtension() {
DateTime date = DateTime.Now;
foreach(System.Globalization.CultureInfo culture in CultureInfo.GetCultures(CultureTypes.UserCustomCulture | CultureTypes.SpecificCultures)) {
Console.WriteLine($"{culture.EnglishName}: {date.ToShortDateString()} First Day of week: {date.StartOfWeek(culture).ToShortDateString()}");
}
}
答案 24 :(得分:0)
如果您想要周六或周日或周中任何一天但不超过当前周(周六至周日),我会为您提供这段代码。
public static DateTime GetDateInCurrentWeek(this DateTime date, DayOfWeek day)
{
var temp = date;
var limit = (int)date.DayOfWeek;
var returnDate = DateTime.MinValue;
if (date.DayOfWeek == day) return date;
for (int i = limit; i < 6; i++)
{
temp = temp.AddDays(1);
if (day == temp.DayOfWeek)
{
returnDate = temp;
break;
}
}
if (returnDate == DateTime.MinValue)
{
for (int i = limit; i > -1; i++)
{
date = date.AddDays(-1);
if (day == date.DayOfWeek)
{
returnDate = date;
break;
}
}
}
return returnDate;
}
答案 25 :(得分:0)
我们喜欢单线型:获取当前区域性的第一天与当日的差值,然后从当日减去天数
var weekStartDate = DateTime.Now.AddDays(-((int)now.DayOfWeek - (int)DateTimeFormatInfo.CurrentInfo.FirstDayOfWeek));
答案 26 :(得分:0)
您可以使用优秀的Umbrella library:
using nVentive.Umbrella.Extensions.Calendar;
DateTime beginning = DateTime.Now.BeginningOfWeek();
但是,他们做似乎已将星期一存储为一周的第一天(请参阅属性nVentive.Umbrella.Extensions.Calendar.DefaultDateTimeCalendarExtensions.WeekBeginsOn
),以便之前的本地化解决方案更好一些。不幸的。
编辑:仔细观察这个问题,看起来Umbrella也可能真的有效:
// Or DateTime.Now.PreviousDay(DayOfWeek.Monday)
DateTime monday = DateTime.Now.PreviousMonday();
DateTime sunday = DateTime.Now.PreviousSunday();
虽然值得注意的是,如果你在星期一要求上一个星期一,它会给你七天的时间。但如果您使用BeginningOfWeek
,这也是正确的,这似乎是一个错误:(。
答案 27 :(得分:0)
根据“编译此答案”,使用以下方法获取星期几的日期:
public static DateTime GetDayOfWeek(this DateTime dt, DayOfWeek day)
{
int diff = (7 + (dt.DayOfWeek - DayOfWeek.Monday)) % 7;
var monday = dt.AddDays(-1 * diff).Date;
switch (day)
{
case DayOfWeek.Tuesday:
return monday.AddDays(1).Date;
case DayOfWeek.Wednesday:
return monday.AddDays(2).Date;
case DayOfWeek.Thursday:
return monday.AddDays(3).Date;
case DayOfWeek.Friday:
return monday.AddDays(4).Date;
case DayOfWeek.Saturday:
return monday.AddDays(5).Date;
case DayOfWeek.Sunday:
return monday.AddDays(6).Date;
}
return monday;
}
答案 28 :(得分:0)
尝试创建使用递归的函数。您的DateTime对象是输入,函数返回一个新的DateTime对象,该对象代表一周的开始。
DateTime WeekBeginning(DateTime input)
{
do
{
if (input.DayOfWeek.ToString() == "Monday")
return input;
else
return WeekBeginning(input.AddDays(-1));
} while (input.DayOfWeek.ToString() == "Monday");
}
答案 29 :(得分:0)
通过这种方式计算,您可以选择一周中的哪一天指示新一周的开始(在我选择的示例中为星期一)。
请注意,对于星期一这一天进行此计算,将得出当前星期一,而不是前一个。
//Replace with whatever input date you want
DateTime inputDate = DateTime.Now;
//For this example, weeks start on Monday
int startOfWeek = (int)DayOfWeek.Monday;
//Calculate the number of days it has been since the start of the week
int daysSinceStartOfWeek = ((int)inputDate.DayOfWeek + 7 - startOfWeek) % 7;
DateTime previousStartOfWeek = inputDate.AddDays(-daysSinceStartOfWeek);
答案 30 :(得分:0)
是星期一,但逻辑是星期天。
public static DateTime GetStartOfWeekDate()
{
// Get today's date
DateTime today = DateTime.Today;
// Get the value for today. DayOfWeek is an enum with 0 being Sunday, 1 Monday, etc
var todayDayOfWeek = (int)today.DayOfWeek;
var dateStartOfWeek = today;
// If today is not Monday, then get the date for Monday
if (todayDayOfWeek != 1)
{
// How many days to get back to Monday from today
var daysToStartOfWeek = (todayDayOfWeek - 1);
// Subtract from today's date the number of days to get to Monday
dateStartOfWeek = today.AddDays(-daysToStartOfWeek);
}
return dateStartOfWeek;
}
答案 31 :(得分:0)
我是这样做的:
DateTime.Now.Date.AddDays(-(DateTime.Now.Date.DayOfWeek == 0 ? 7 : (int)DateTime.Now.Date.DayOfWeek) + 1)
这段代码所做的就是从给定的日期时间中减去天数。
如果星期几为 0(星期日),则减去 7,否则减去星期几。
然后在上一行的结果上加 1 天,这就是该日期的星期一。
通过这种方式,您可以使用末尾的数字 (1) 来获得所需的日期。
private static DateTime GetDay(DateTime date, int daysAmount = 1)
{
return date.Date.AddDays(-(date.Date.DayOfWeek == 0 ? 7 : (int)date.Date.DayOfWeek) + daysAmount);
}
如果你真的想使用 DayOfWeek 枚举,那么可以使用这样的东西......虽然我个人更喜欢上面的那个,因为我可以添加或减去任何天数。
private static DateTime GetDayOfWeek(DateTime date, DayOfWeek dayOfWeek = DayOfWeek.Monday)
{
return date.Date.AddDays(-(date.Date.DayOfWeek == 0 ? 7 : (int)date.Date.DayOfWeek) + (dayOfWeek == 0 ? 7 : (int)dayOfWeek));
}
答案 32 :(得分:-1)
d = DateTime.Now;
int dayofweek =(int) d.DayOfWeek;
if (dayofweek != 0)
{
d = d.AddDays(1 - dayofweek);
}
else { d = d.AddDays(-6); }
答案 33 :(得分:-2)
public static System.DateTime getstartweek()
{
System.DateTime dt = System.DateTime.Now;
System.DayOfWeek dmon = System.DayOfWeek.Monday;
int span = dt.DayOfWeek - dmon;
dt = dt.AddDays(-span);
return dt;
}