for i as integer =  0  to MyCollection.Count -  1 
   .....
 end for

for i as integer = MyCollection.Count to  0  step - 1 
   .....
end for

'либо

dim ub as Integer
ub = MyCollection.Count -  1 
 for i as integer =  0  to ub
   .....
 end for

 Dim col As New Collection

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        For i As Int32 =  0  To  100000 
            col.Add(i)
        Next
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim t As Long = Now.Ticks

        Dim v As Int32
        For Each i As Int32 In col
            v = i
        Next

        MsgBox("done in " + (Now.Ticks - t).ToString + " tiсks")
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Dim ub As Int32 = col.Count -  1 
        Dim t As Long = Now.Ticks
        Dim v As Int32
        For i As Int32 =  0  To ub
            v = i
        Next
        MsgBox("done in " + (Now.Ticks - t).ToString + " tiсks")
    End Sub