ต้องการให้เลขที่เอกสารมัน+เพิ่มทีละ 1 แต่ลองแล้วไม่ยอม+ให้

Private Sub AutoGenerateID()
        Dim sqlTmp As String = ""
        Dim comTmp As New SqlClient.SqlCommand
        Dim drTmp As SqlClient.SqlDataReader
        Dim tmpMemberID As Integer = 0

        sqlTmp = "SELECT TOP 1 OrderID FROM OrderBuy ORDER BY CAST(OrderID AS int) DESC"
         If (DbConn.State = ConnectionState.Closed) Then
            DbConn.Open()
        End If
        Try
            With comTmp
                .CommandType = CommandType.Text
                .CommandText = sqlTmp
                .Connection = DbConn
                drTmp = .ExecuteReader()
                drTmp.Read()
                orderID.Text = CInt(drTmp.Item("OrderID") + 1)
                tmpMemberID = CInt(drTmp.Item("OrderID"))
                tmpMemberID = tmpMemberID + 1
                orderID.Text = strDate & strMonth & "-" & tmpMemberID.ToString("0000") 
            End With
        Catch
            orderID.Text = strDate & strMonth & "-" & "0001"   '5409-0001
            DbConn.Close()
        End Try
    End Sub

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