Skip to main content

Common .Net Interview Questions and Why are they asked?

There are many .Net Questions that every interviewer(in general) asks.
Through this, I am starting a series of discussions where in I'll be discussing these questions and provide ample satisfactory answers to them.

The intent here is to realise the importance of these questions and help the needy(those who are preparing for interviews) and also who believe in knowing the basics rather than just blindly implementing the .Net classes/Interfaces.

Starting the First part of this series is All time Classic question #1

Question: What is the difference between Abstract Classes and Interface?

The moment this question is asked the candidates generally start uttering the bookish definitions, some of them are .
a) Access modifiers: Interfaces--Implicitly Public() , Classes can use use Access Modifiers.
b) No implementation in Interfaces, Classes can have implementations as well.
c)Abstract classes can't be instantiated .

Some more experienced candidates might get into some further details, However the basic things to understand here is  if these two are that much close in implementing functionality why do we have these two separately in C#

I'm not trying to be an Expert here, all I am trying, is to get rid of this anxious question once for all by exploring it from some possible angles.

OOPS principle that is being tested by this question: Polymorphism

Without going into Polymorphism details, both of these(Interfaces and Abstract Classes) are a ways of achieving Polymorphism in the Code.

Let's consider an example

public void Gadgets(MyGadget gadget){

}

This method could accept any object that implemented MyGadget as the gadget argument, even though the implementations of MyGadget might be quite different.

 A Class may inherit from only one base class(in C# ), so if you want to use abstract classes to provide polymorphism to a group of classes, they must all inherit from that class.
Abstract classes may also provide members that have already been implemented. Therefore, you can ensure a certain amount of identical functionality with an abstract class, but cannot with an interface.

 Decide whether to use an interface or an abstract class to provide polymorphism for your components.

  • If creating multiple versions of your component is anticipated, create an abstract class. Abstract classes provide a simple and easy way to version components. By updating the base class, all inheriting classes are automatically updated with the change. Interfaces, on the other hand, cannot be changed once created. If a new version of an interface is required,  a whole new interface must be created.

  • If the functionality youbeing created will be useful across a wide range of disparate objects, use an interface. Abstract classes should be used primarily for objects that are closely related, whereas interfaces are best suited for providing common functionality to unrelated classes.

  • If designing small, concise bits of functionality, use interfaces. If  designing large functional units, use an abstract class.

  • If  common, implemented functionality among all implementations of the component is intended, use an abstract class. Abstract classes allow to partially implement class, whereas interfaces contain no implementation for any members.


Hope this helps in making the decision as to when to use interfaces and when to use Abstract Classes,

Soon, I'll try to cover other commonly asked interview question.

Till next we connect, Happy Coding.

 
Labels:

Comments

Post a Comment

Popular posts from this blog

Asp.Net 4.0: An Overview-Part-III

This is the last post in the series which will explore the following new features of ASP.Net 4.0  Performance Monitoring for Individual Applications in a Single Worker Process Web.config File Refactoring Permanently Redirecting a Page Expanding the Range of Allowable URLs Performance Monitoring for Individual Applications in a Single Worker Process It is a common practice to host multiple ASP.NET applications in a single worker process, In order to increase the number of Web sites that can be hosted on a single server. This practice results in difficulties for server administrators to identify an individual application that is experiencing problems. ASP.NET 4 introduces new resource-monitoring functionality introduced by the CLR. To enable this functionality, following XML configuration snippet is added to the aspnet.config configuration file.(This file is located in the directory where the .NET Framework is installed ) <?xml version="1.0" encoding="UTF-8...
Post a Comment
Read more

WCF-REST Services-Part-II

HOW REST is implemented in WCF Part-I of the series explored the REST conceptually and this post will explore how REST is implemented in WCF. For REST implementation in WCF, 2 new attributes namely WebGetAttribute and WebInvokeAttribute are introduced in WCF along with a URI template mechanism that enables you to declare the URI and verb to which each method is going to respond. The infrastructure comes in the form of a binding ( WebHttpBinding ) and a behavior ( WebHttpBehavior ) that provide the correct networking stack for using REST. Also, there is some hosting infrastructure help from a custom Service¬Host ( WebServiceHost ) and a ServiceHostFactory ( WebServiceHostFactory ). How WCF Routes messages WCF routes network messages to methods on instances of the classes defined as implementations of the service. Default behavior ( Dispatching ) for WCF is to do this routing based on the concept of action. For this dispatching to work, an action needs to be present in ev...
Post a Comment
Read more

WPF Routing

WPF (3.5) introduced the concept of Routing that made the event routing easies in the scenarios where it was tedious to handle events. Consider a scenario where there are a number of Hyperlinks in a Panel that direct to separate locations on Click. Now if this is done in normal programming, each hyperlink will have to have code for execution. It would be easier and cleaner if we could handle the hyperlinks in the container (the Panel) that handles the click and redirects to appropriate location. WPF handles the events with the following 3 strategies. Direct events are like ordinary .NET events. They originate in one element and don’t pass to any other. For example, MouseEnter is a direct event. Bubbling events are events that travel up the containment hierarchy. For example, MouseDown is a bubbling event. It is raised first by the element that is clicked. Next, it is raised by that element’s parent, and then by that element’s parent, and so on, until WPF reaches the top of the e...
Post a Comment
Read more