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);

使用扩展方法:

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;
    }
}

可以这样使用:

DateTime dt = DateTime.Now.StartOfWeek(DayOfWeek.Monday);
DateTime dt = DateTime.Now.StartOfWeek(DayOfWeek.Sunday);

你可以使用优秀的Umbrella库:

using nVentive.Umbrella.Extensions.Calendar;
DateTime beginning = DateTime.Now.BeginningOfWeek();

然而，它们似乎已经将星期一存储为一周的第一天(参见属性nvent . umbrelga . extensions . calendar . defaultdatetimecalendarexextensions . weekbeginson)，因此先前的本地化解决方案要好一些。不幸的。

编辑:仔细看看这个问题，雨伞似乎也能解决这个问题:

// Or DateTime.Now.PreviousDay(DayOfWeek.Monday)
DateTime monday = DateTime.Now.PreviousMonday(); 
DateTime sunday = DateTime.Now.PreviousSunday();

尽管值得注意的是，如果你在周一要求前一个周一，它会给你7天。但如果你使用BeginningOfWeek，这也是正确的，这似乎是一个错误:(。

这将返回一周的开始和结束日期:

    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;

    }

我已经在我的博客上发布了计算周、月、季度和年的开始/结束的完整代码 ZamirsBlog

如果您需要周六、周日或一周中的任何一天，但不超过当前一周(周六-日)，我用这段代码为您提供了支持。

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;
}

周一

DateTime startAtMonday = DateTime.Now.AddDays(DayOfWeek.Monday - DateTime.Now.DayOfWeek);

在周日

DateTime startAtSunday = DateTime.Now.AddDays(DayOfWeek.Sunday- DateTime.Now.DayOfWeek);