Question

NOTE: I tried using concat() method, join method and even tried to
insert just text(which turned out editable) but none of them worked as
I wanted. I was thinking if substring method will work but I only have
basic idea of how substring works. I want the letter “N” to be
inserted into the text box when form loads and when the user enters
4digits(OrderNo2.text) which should be joined so that it can be saved
together when I clicked on save button.

Please help guys. Thanks

Private Sub btnAddOrder_Click(ByVal sender As System.Object, ByVal e
  As System.EventArgs) Handles btnAddOrder.Click



isNewRow = True
        Dim newRow As DataRow = dsOrders.Tables("Orders").NewRow

        Try
            If txtOrderNo2.Text.Length = 5 Then
                newRow.Item("OrderNo") = txtOrderNo2.Text
                If cbo_Product.SelectedIndex <> -1 Then
                    newRow.Item("Product") = cbo_Product.Text
                    newRow.Item("Price") = txtPrice2.Text
                    If txtQuantity.Text <> "" Then
                        newRow.Item("Quantity") = txtQuantity.Text
                        newRow.Item("CustomerNo") = txtCustomerNo2.Text
                        dsOrders.Tables("Orders").Rows.Add(newRow)
                        'determine row index of new row
                        rowIndex = dsOrders.Tables("Orders").Rows.Count - 1
                        'save changes back to the database
                        daOrders.Update(dsOrders, "Orders")

                    Else
                        MessageBox.Show("Please enter the quantity", "Missing Quantity", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
                    End If
                Else
                    MessageBox.Show("Please choose the product", "Missing Price", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
                End If
            Else
                MessageBox.Show("Order Number must be 5 digits long!", "Missing Order Number", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
            End If

        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try

    End Sub

Answer 1

Used a MaskedTextBox instead of a regular TextBox. You can then set the Mask property to "N0000", which will only allow the user to enter 4 digits following the 'N', and will not let the user edit the 'N'. The Text property will give you the displayed text, including the 'N'.