Finding the date of monday in a week with VB.NET

Question

I need to find a way to find the date (DD/MM/YYYY) of the Monday for any week we\'re on.

For example, for this week, monday would be 09/11/2009, and if this were nex

Answer 1

Following on from my comments to Meta-Knight's answer, here is a short function that makes the correction I mention in the comments:

Public Function GetFirstOfLastWeek() As DateTime
Dim today As DateTime, daysSinceMonday As Integer
    today = DateTime.Today
    daysSinceMonday = today.DayOfWeek - DayOfWeek.Monday
    If daysSinceMonday < 0 Then
        daysSinceMonday += 7
    End If
    Return today.AddDays(-daysSinceMonday)  
End Function

Answer 2

And if your week starts from Monday then you can use something like this:

DateTime mondayDate = DateTime.Now.AddDays(((DateTime.Now.DayOfWeek == DayOfWeek.Sunday?7: (int)DateTime.Now.DayOfWeek) - 1)*-1);

DateTime sundayDate = DateTime.Now.AddDays(7 - (DateTime.Now.DayOfWeek == DayOfWeek.Sunday?7: (int)DateTime.Now.DayOfWeek ));

Answer 3

If Sunday is the first day of week, you can simply do this:

Dim today As Date = Date.Today
Dim dayDiff As Integer = today.DayOfWeek - DayOfWeek.Monday
Dim monday As Date = today.AddDays(-dayDiff)

If Monday is the first day of week:

Dim today As Date = Date.Today
Dim dayIndex As Integer = today.DayOfWeek
If dayIndex < DayOfWeek.Monday Then
    dayIndex += 7 'Monday is first day of week, no day of week should have a smaller index
End If
Dim dayDiff As Integer = dayIndex - DayOfWeek.Monday
Dim monday As Date = today.AddDays(-dayDiff)

Answer 4

Another approach if Monday is the first day, is this:

 Dim today As Date = Date.Today
                Dim dayDiff As Integer = today.DayOfWeek - DayOfWeek.Monday
                Dim monday As Date = today.AddDays(-dayDiff)

                dayDiff = DayOfWeek.Saturday - today.DayOfWeek + 1
                Dim sunday As Date = today.AddDays(dayDiff)