VB - Datum des Montags einer Woche berechnen

'Imports System.Globalization

Private Function GetMondayDateOfWeek(week As Integer, year As Integer) As DateTime
    Dim i As Integer = CultureInfo.CurrentCulture.Calendar.GetWeekOfYear(New DateTime(year, 1, 1), CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Monday)

    If i = 1 Then
        Return CultureInfo.CurrentCulture.Calendar.AddDays(New DateTime(year, 1, 1), ((week - 1) * 7 - GetDayCountFromMonday(CultureInfo.CurrentCulture.Calendar.GetDayOfWeek(New DateTime(year, 1, 1))) + 1))
    Else
        Dim x As Integer = Convert.ToInt32(CultureInfo.CurrentCulture.Calendar.GetDayOfWeek(New DateTime(year, 1, 1)))
        Return CultureInfo.CurrentCulture.Calendar.AddDays(New DateTime(year, 1, 1), ((week - 1) * 7 + (7 - GetDayCountFromMonday(CultureInfo.CurrentCulture.Calendar.GetDayOfWeek(New DateTime(year, 1, 1)))) + 1))
    End If
End Function

'Gibt den Wochentag als Zahl zurück, Montag entspricht 1
Private Function GetDayCountFromMonday(dow As DayOfWeek) As Integer
    Select Case dow
        Case DayOfWeek.Monday
            Return 1
        Case DayOfWeek.Tuesday
            Return 2
        Case DayOfWeek.Wednesday
            Return 3
        Case DayOfWeek.Thursday
            Return 4
        Case DayOfWeek.Friday
            Return 5
        Case DayOfWeek.Saturday
            Return 6
        Case Else
            'Sunday
            Return 7
    End Select
End Function