我如何在c#中找到一周的开始(包括周日和周一),只知道当前时间?
喜欢的东西:
DateTime.Now.StartWeek(Monday);
我如何在c#中找到一周的开始(包括周日和周一),只知道当前时间?
喜欢的东西:
DateTime.Now.StartWeek(Monday);
当前回答
我尝试了几次,但我没有解决从星期一开始的一周的问题,导致我的下一个星期一是星期天。所以我对它做了一些修改,让它与下面的代码一起工作:
int delta = DayOfWeek.Monday - DateTime.Now.DayOfWeek;
DateTime monday = DateTime.Now.AddDays(delta == 1 ? -6 : delta);
return monday;
其他回答
步骤1:
创建静态类
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;
}
}
第二步:使用这个类来确定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);
我能想到的最快方法是:
var sunday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek);
如果您希望将一周中的任何一天作为您的开始日期,您所需要做的就是在结束时添加DayOfWeek值
var monday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek + (int)DayOfWeek.Monday);
var tuesday = DateTime.Today.AddDays(-(int)DateTime.Today.DayOfWeek + (int)DayOfWeek.Tuesday);
下面的方法应该返回所需的DateTime。周日为true,周一为false:
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);
}
通过这种方式计算,您可以选择一周中的哪一天表示新一周的开始(在示例中,我选择了星期一)。
请注意,对星期一进行这个计算将得到当前的星期一,而不是以前的星期一。
//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);
这可能有点黑,但你可以将. dayofweek属性转换为int(它是一个枚举,因为它的底层数据类型没有改变,它默认为int),并使用它来确定一周的前一周。
它显示DayOfWeek枚举中指定的周从周日开始,因此如果将这个值减去1,就等于周一离当前日期有多少天。我们还需要将周日(0)映射为7,因此给定1 - 7 = -6,周日将映射到前一个周一:-
DateTime now = DateTime.Now;
int dayOfWeek = (int)now.DayOfWeek;
dayOfWeek = dayOfWeek == 0 ? 7 : dayOfWeek;
DateTime startOfWeek = now.AddDays(1 - (int)now.DayOfWeek);
前一个星期天的代码更简单,因为我们不需要做这样的调整:-
DateTime now = DateTime.Now;
int dayOfWeek = (int)now.DayOfWeek;
DateTime startOfWeek = now.AddDays(-(int)now.DayOfWeek);