[silverlight]

كود :

Public Class Form1

    Private first As FirstCustomer
    Private second As SecondCutomer

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

        first = New FirstCustomer
        second = New SecondCutomer

        Dim item1 As Double = 2
        Dim item2 As Double = 4
        Dim item3 As Double = 6

        Me.ListBox1.Items.Add(first.Calculate(item1, item2))
        first.Name = "ahmed"
        Me.ListBox1.Items.Add(first.Name)
    End Sub

End Class

Public Class Person
    Private _name As String

    Public Sub New()
        Me._name = Nothing
    End Sub

    Public Property Name As String
        Get
            Return Me._name
        End Get
        Set(value As String)
            Me._name = value
        End Set
    End Property

    Public Function Calculate(firstItem As Double, SecondItem As Double)
        Return firstItem + SecondItem
    End Function

    Public Function Calculate(firstItem As Double, SecondItem As Double, thirdItem As Integer)
        Return firstItem + SecondItem + thirdItem
    End Function

End Class

Public Class FirstCustomer
    Inherits Person
End Class

Public Class SecondCutomer
    Inherits Person

    Private _number As String

    Public Sub New()
        Me._number = Nothing
    End Sub

    Public Property Number As String
        Get
            Return Me._number
        End Get
        Set(value As String)
            Me._number = value
        End Set
    End Property

End Class