First, why do you have this? strSelection = boConversionType.SelectedIndex.ToString()
Second.
I can see what the code does, but I can't see what strSelection is for.
If you select something from the combobox, the SelectedIndex will be > -1.
So, the Select Case statement works as it should.
You might wanna consider adding a Case Else for a default value in case you forget to select something.
What Select Case does is that it checks the value of whatever argument you put to it.
And then each Case checks if the value is this or that.
It's just a compressed version of If...Else If...Else If...Else If...Else...End If.
'These two examples perform the EXACT same task, but the first one is bit more bulkier
If cboConverstionType.SelectedIndex = 0 Then
strSelection = 25
Else If cboConverstionType.SelectedIndex = 1 Then
strSelection = 30
Else If cboConverstionType.SelectedIndex = 2 Then
strSelection = 35
End If
Select Case cboConverstionType.SelectedIndex
Case 0
strSelection = 25
Case 1
strSelection = 30
Case 2
strSelection = 35
End Select