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What is the Purpose of "explicit" Implementation of Interface?

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1 Jun 2014CPOL1 min read 15.6K   4   5
Purpose of "Explicit" Implementation of Interface in C#

Introduction

There are 2 types of interface implementations available in C#. One is Implicit and another one is Explicit. This tip explains the purpose of the "Explicit" implementation of Interfaces.

Background

Interfaces are the one of the best language features in C#, which helps to achieve the run time polymorphic feature. Every programmer has experience with interfaces, with implicit implementation, which is normal. This article talks about another way of implementation and its purposes.

Using the Code

There are 2 purposes of explicit implementation of Interface:
First, it is used to avoid name collision between interface methods. That is if you are going to create a class library, there may be a chance to use the same name in several places. At that time "explicit" implementation comes as a rescue.
Secondly, You cannot access that implemented method through the object of the class directly. Instead you typecast it as Interface reference then you can access it. This is because, the C# compiler, unable to determine which one the user want to call.

In another way, you need to add "public" access specifier in the interface's implemented method in a class. But if you "explicitly" implemented the interface, you can change this one. That means, it will be look alike private method. But with one exception, you can access that explicit implemented method through the reference of the interface. Please take a look at the below code for a detailed explanation:

C#
interface ISample
{
    void method1();
    void method2();
}

interface IAnotherSample
{
    void method1();
}

class A : ISample, IAnotherSample
{
    // Explicit implementation avoid name collision
    void ISample.method1()
    {
    }
    void IAnotherSample.method1()
    {
    }
    // Implicit implementation
    public void method2()
    {
    }
}

// Inherit Class A
class B : A
{
    // Create Object for class A
    A obj = new A();
    B()
    {
        // You can call method2
        obj.method2();
        // Error: You cannot call method1 Since Explicit implementation
        //obj.method1();
        // But you can access it by Interface Reference
        ((ISample)obj).method1();
    }
}

Finally, one more point, explicitly implemented interfaces' methods are not listed down in the Visual Studio IDE's intellisense.

Image 1

Readers, do you have any thoughts/opinions, please write your comments below!!

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Software Developer (Senior)
India India
Hi All, I am Francis from India. Working as a Senior Software Engineer. I have 6+ Years of experience in ASP.Net and C#/VB.Net. Also founder of ASPDotNetChamp, where i blog my day to day ASP.Net Experiences, Problems and Interview Questions.

Comments and Discussions

 
QuestionAre name collisions the only reason? Pin
cjb1101-Jun-14 21:11
cjb1101-Jun-14 21:11 
AnswerRe: Are name collisions the only reason? Pin
Francis S Michael2-Jun-14 0:17
professionalFrancis S Michael2-Jun-14 0:17 
Hi cjb,

Thanks for your valuable comment. Avoiding name collision is the first reason. Some of the C# programmers also suggest always go with Explicit implementation. since it keeps the code clear. That means you can easily identify which method depends on which interface.

Hope this helps!

GeneralRe: Are name collisions the only reason? Pin
Menci Lucio2-Jun-14 23:34
professionalMenci Lucio2-Jun-14 23:34 
GeneralThanks.. Pin
RhishikeshLathe1-Jun-14 20:33
professionalRhishikeshLathe1-Jun-14 20:33 
GeneralRe: Thanks.. Pin
Francis S Michael1-Jun-14 20:57
professionalFrancis S Michael1-Jun-14 20:57 

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