Code Snippet: Calculating the first date of the week for a given date & a given week start

I know I’m going to need to use this again at some point & it took me an hour and a half to figure this one out. I can’t believe .NET 2.0 doesn’t have a built-in method to do this…?


// C#
public DateTime GetStartOfWeek(DateTime date, DayOfWeek WeekStartDay) {
double daysToStart = (Convert.ToDouble(today.DayOfWeek) - Convert.ToDouble(WeekStartDay) + 7) % 7;
DateTime weekStartDate = date.AddDays(0 - daysToStart);
return weekStartDate;
}