Interfaces in vb.net

Interfaces

Interfaces allow us to create definitions for component interaction. They also provide another way of implementing polymorphism. Through interfaces, we specify methods that a component must implement without actually specifying how the method is implemented. We just specify the methods in an interface and leave it to the class to implement those methods. Visual Basic .NET does not support multiple inheritance directly but using interfaces we can achieve multiple inheritance. We use the Interface keyword to create an interface and implements keyword to implement the interface. Once you create an interface you need to implement all the methods specified in that interface. The following code demonstrates the use of interface.

Imports System.Console Module Module1 Sub Main() Dim OneObj As New One() Dim TwoObj As New Two() 'creating objects of class One and Two OneObj.disp() OneObj.multiply() TwoObj.disp() TwoObj.multiply() 'accessing the methods from classes as specified in the interface End Sub End Module Public Interface Test 'creating an Interface named Test Sub disp() Function Multiply() As Double 'specifying two methods in an interface End Interface Public Class One    Implements Test 'implementing interface in class One Public i As Double = 12 Public j As Double = 12.17 Sub disp() Implements Test.disp 'implementing the method specified in interface WriteLine("sum of i+j is" & i + j) Read() End Sub Public Function multiply() As Double Implements Test.Multiply 'implementing the method specified in interface WriteLine(i * j) Read() End Function End Class Public Class Two    Implements Test 'implementing the interface in class Two Public a As Double = 20 Public b As Double = 32.17 Sub disp() Implements Test.disp WriteLine("Welcome to Interfaces") Read() End Sub Public Function multiply() As Double Implements Test.Multiply WriteLine(a * b) Read() End Function End Class

Output of above code is shown in  image