Use Is and As to convert a class to its implenented Interface : Is « Operator « VB.Net Tutorial

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VB.Net Tutorial » Operator » Is 
3. 9. 2. Use Is and As to convert a class to its implenented Interface
 
 

 Imports System

     Interface Printable
         Sub Read( )
         Sub Write(ByVal obj As Object)

         Property Status( ) As Integer
     End Interface 

     Interface Zippable
         Sub Zip( )
         Sub Unzip( )
     End Interface 

     Public Class Document 
     Implements Printable

         Public Sub New(ByVal s As String)
             Console.WriteLine("Creating document with: {0}", s)
         End Sub 

         Public Sub Read( ) Implements Printable.Read
             Console.WriteLine("Implementing the Read Method for Printable")
         End Sub 

         Public Sub Write(ByVal o As ObjectImplements Printable.Write
             Console.WriteLine("Implementing the Write Method for Printable")
         End Sub 'Write

         Public Property Status( ) As Integer Implements Printable.Status
             Get
                 Return Status
             End Get
             Set(ByVal Value As Integer)
                 Status = Value
             End Set
         End Property
         Private myStatus As Integer = 0
     End Class 'Document

     Class Tester
         Public Sub Run( )
         End Sub 'Run

         Shared Sub Main( )
             Dim doc As New Document("Test Document")

             If TypeOf doc Is Printable Then
                 Dim isDoc As Printable = doc
                 isDoc.Read( )
             Else
                 Console.WriteLine("Could not cast to Printable")
             End If

             If TypeOf doc Is Zippable Then
                 Dim icDoc As Zippable = doc
                 icDoc.Zip( )
             Else
                 Console.WriteLine("Could not cast to Zippable")
             End If
         End Sub 'Main

     End Class

        
  
  




Creating document with: Test Document
Implementing the Read Method for Printable
Could not cast to Zippable

 
3. 9. Is
3. 9. 1. Demonstrate 'is a' relationship
3. 9. 2. Use Is and As to convert a class to its implenented Interface
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