Set last week's Monday as defaul in dropwdown in VB.NET - asp.net

Question

I have a dropdown which I have to populate with the last 5 Mondays, but I need to set the Monday of the previos week set as default
I have the following code to create a list of the last 5 Mondays
Public Sub GetMondays()
'populate the dateselection with the last 5 mondays to show the week starting
Dim dtMondays As New DataTable()
dtMondays.Columns.Add("Date")
Dim i As Integer = 1
Dim count As Integer
While (count < 5)
Dim Day As DateTime = Today.AddDays(-i)
If Day.DayOfWeek = 1 Then
DateSelection.Items.Add(New ListItem(Format(Day, "dd/MMM/yyyy"), Day))
count = count + 1
End If
i += 1
End While
End Sub
If today is the 26th of May 2014 I would see the 10th of May and the following full list in the dropdown:
19/05/2014 > Displayed
12/05/2014
05/05/2014
28/04/2014
21/04/2014
If today is the 27th of May 2014 I would see the 10th of May and the following full list in the dropdown:
26/05/2014 > Displayed
19/05/2014 > This one should be displayed
12/05/2014
05/05/2014
28/04/2014
What I need is to keep the order as per above, have the previous Monday selected in the dropdown as per above.
Any ideas on how to do this
Thanks

Answer 1

Compare week number for today and the first item in the list
GetMondays()
Dim c As Calendar = DateTimeFormatInfo.CurrentInfo.Calendar
If c.GetWeekOfYear(Today, CalendarWeekRule.FirstDay, DayOfWeek.Monday) _
= c.GetWeekOfYear(DateSelection.Items(0).Text, CalendarWeekRule.FirstDay, DayOfWeek.Monday) Then
DateSelection.SelectedIndex = 1
Else
DateSelection.SelectedIndex = 0
End If
if week number is the same (e.g. "27/05/2014" and "26/05/2014" will have same week number) then change selection to the second item (SelectedIndex = 1)
P.S.
You can also try more efficient code to populate the list. It does not need to enumerate each day in 4 weeks to find Mondays. You only need to find last Monday and then you can use AddDays(-7) to get a week back.
'Dim count As Integer
'While (count < 5)
' Dim Day As DateTime = (Today.AddDays(1)).AddDays(-i)
' If Day.DayOfWeek = 1 Then
' 'DateSelection.Items.Add(New ListItem(Format(Day, "dd/MMM/yyyy"), Day))
' Console.WriteLine(Format(Day, "dd/MMM/yyyy"), Day)
' count = count + 1
' End If
' i += 1
'End While
Dim Day As Date = Today.AddDays(-(Today.DayOfWeek - DayOfWeek.Monday))
For count As Integer = 1 To 4
DateSelection.Items.Add(New ListItem(Format(Day, "dd/MMM/yyyy"), Day))
Day = Day.AddDays(-7)
Next