Perulangan Do While Pada VB.net

Public Class Perulangan_Do_while

    Private Sub Perulangan_Do_while_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim a As Byte
        a = 1
        Do While a <= 10
            ComboBox2.Items.Add(a)
            a = a + 1
        Loop
        Dim c As Byte
        c = 65
        Do While c <= 90
            ComboBox3.Items.Add(Chr(c))
            c = Val(c + 1)
        Loop
        Dim b As Byte
        b = 10
        Do While b >= 1
            ComboBox1.Items.Add(b)
            b = b - 1
        Loop
    End Sub
End Class