我如何获取一周中开始的DateTime？

使用扩展方法。他们是一切的答案，你知道的！;）

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;    }}

可以如下使用：

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