[سؤال] ارجو مساعدتي بالاجابة عن سؤال

كود :

'كود جلب أسماء كل الطابعات المثبتة على الجهاز

Public Sub LoadAllPrinters()

    For Each Name As String In Printing.PrinterSettings.InstalledPrinters

        ComboBox1.Items.Add(Name)

    Next

    Dim PrintDoc As New Printing.PrintDocument()

    ComboBox1.Text = PrintDoc.PrinterSettings.PrinterName

End Sub

'كود تعيين الطابعة الافتراضية

Public Function SetDefaultPrinter(ByVal Name As String) As Boolean

    Dim PrintDoc As New Printing.PrintDocument()

    Dim WshNetwork As Object = Nothing

    Dim OldPrinterName As String = String.Empty

    Try

        OldPrinterName = PrintDoc.PrinterSettings.PrinterName

        WshNetwork = Microsoft.VisualBasic.CreateObject("WScript.Network")

        WshNetwork.SetDefaultPrinter(Name)

        PrintDoc.PrinterSettings.PrinterName = Name

        If PrintDoc.PrinterSettings.IsValid Then

            Return True

        Else

            WshNetwork.SetDefaultPrinter(OldPrinterName)

            Return False

        End If

    Catch ex As Exception

        If WshNetwork IsNot Nothing Then

            WshNetwork.SetDefaultPrinter(OldPrinterName)

        End If

    Finally

        PrintDoc = Nothing

        WshNetwork = Nothing

    End Try

    Return False

End Function

Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

    LoadAllPrinters()

End Sub

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

    If SetDefaultPrinter(ComboBox1.Text) Then

        MessageBox.Show(String.Format("الطابعة ""{0}"" أصبحت هي الطابعة الافتراضية", ComboBox1.Text),

                        "الطابعة", MessageBoxButtons.OK, MessageBoxIcon.Information,

                        MessageBoxDefaultButton.Button1, MessageBoxOptions.RtlReading)

    End If

End Sub