What is a Interface ?

Interface is a contract that defines the signature of the functionality. So if a class is implementing a interface it says to the outer world, that it provides specific behavior. Example if a class is implementing Idisposable interface that means it has a functionality to release unmanaged resources. Now external objects using this class know that it has contract by which it can dispose unused unmanaged objects.
ã Single Class can implement multiple interfaces.
ã If a class implements a interface then it has to provide implementation to all its methods.
In sample there are two files.One has the interface definition and other class implements the interface. Below is the source code “IInterface” is the interface and “ClsDosomething” implements the “IInterface”. This sample just displays a simple message box.

Public Interface IInterFace
Sub DoSomething()
End Interface
Public Class ClsDoSomething
Implements IInterFace
Public Sub DoSomething() Implements
WindowsInterFace.IInterFace.DoSomething
MsgBox(“Interface implemented”)
End Sub
End Class