ช่วยเขียนโค้ด VB.NET ให้หนูด้วยนะค่ะ ข้อนี้ยากจริงๆค่ะ TOT

Function fac(ByVal n As Integer)
        If n < 3 Then
            Return n
        Else
            Return n * fac(n - 1)

        End If
    End Function
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        If ListBox1.SelectedItem.Text = "For next" Then
            Dim count As Integer
            Dim n As Integer
            n = Val(TextBox1.Text)
            For count = 1 To n
                Label5.Text = fac(count)
            Next

        ElseIf ListBox1.SelectedItem.Text = "Do wheile loop" Then
            Dim count As Integer = 1
            Dim a As Integer
            Dim total As Integer
            a = Val(TextBox1.Text)
            Do While a >= count
                total = a * count
                count = count + 1
                Label5.Text = total
            Loop
        End If
    End Sub
End Class

ListBox1.SelectedItem