How to: Create and Implement Interfaces

As explained in Interfaces Overview, interfaces describe the properties, methods, and events of a class without providing any implementation.

To create an interface

1. Define your interface by adding code to it that begins with the Interface keyword and the name of the interface, and ends with the End Interface statement. For example, the following code defines an interface named IAsset.

   Interface IAsset
   End Interface
   

2. Add statements that define the properties, methods, and events your interface supports. For example, the following code defines one function, one property, and one event.

   Interface IAsset
       Event ComittedChange(ByVal Success As Boolean)
       Property Division() As String 
       Function GetID() As Integer 
   End Interface
   

To implement an interface

1. If the interface that you are implementing is not part of your project, add a reference to the assembly containing the interface.

2. Create a new class that implements your interface, and include the Implements keyword in the line following the class name. For example, to implement the IAsset interface, you could name the implementation class Computer, as in the following code.

   Class Computer
       Implements IAsset
   End Class
   

3. Add procedures to implement the properties, methods, and events of the class as in the following code, which builds on the example in the previous step:

   Class Computer
       Implements IAsset
   
       Public Event ComittedChange(ByVal Success As Boolean) _
          Implements IAsset.ComittedChange
   
       Private divisionValue As String 
   
       Public Property Division() As String _
           Implements IAsset.Division
   
           Get 
               Return divisionValue
           End Get 
           Set(ByVal value As String)
               divisionValue = value
               RaiseEvent ComittedChange(True)
           End Set 
       End Property 
   
       Private IDValue As Integer 
   
       Public Function GetID() As Integer _
           Implements IAsset.GetID
   
           Return IDValue
       End Function 
   
       Public Sub New(ByVal Division As String, ByVal ID As Integer)
           Me.divisionValue = Division
           Me.IDValue = ID
       End Sub 
   End Class
   

See Also

Tasks

Walkthrough: Creating and Implementing Interfaces

Concepts

Interfaces Overview

Interface Definition

Implements Keyword and Implements Statement

Interface Implementation Examples in Visual Basic

When to Use Interfaces

Reference

Interface Statement (Visual Basic)

Declaration Contexts and Default Access Levels

Other Resources

Inheritance in Visual Basic