Option Strict On
Imports System
MustInherit Public Class Control
Public Sub New(top As Integer, left As Integer)
Me.top = top
Me.left = left
End Sub
Public MustOverride Sub DrawControl( )
Protected top As Integer
Protected left As Integer
End Class
Public Class Label
Inherits Control
Public Sub New(top As Integer, left As Integer, contents As String)
MyBase.New(top, left)
listBoxContents = contents
End Sub
Public Overrides Sub DrawControl( )
Console.WriteLine("Writing string to the listbox: {0}", listBoxContents)
End Sub
Private listBoxContents As String
End Class
Public Class Button
Inherits Control
Public Sub New(top As Integer, left As Integer)
MyBase.New(top, left)
End Sub
Public Overrides Sub DrawControl( )
Console.WriteLine("Drawing a button at {0}, {1}" + ControlChars.Lf, top, left)
End Sub
End Class
Public Class Tester
Shared Sub Main( )
Dim winArray(3) As Control
winArray(0) = New Label(1, 2, "A")
winArray(1) = New Label(3, 4, "B")
winArray(2) = New Button(5, 6)
Dim i As Integer
For i = 0 To 2
winArray(i).DrawControl( )
Next i
End Sub 'Main
End Class 'Tester
Writing string to the listbox: A
Writing string to the listbox: B
Drawing a button at 5, 6