What’s the difference between an interface and abstract class?
nikhil kansal
Select an image from your device to upload
An abstract class is a class that can not be instantiated but that can contain code. An interface only contains method definitions but does not contain any code. With an interface, you need to implement all the methods defined in the interface.
If you have logic that will be the same for all the derived classes, it is best to go for a abstract class in stead of an interface.
You can implement multiple interfaces but only inherit from one class.
________________________________________________________________
Abroad Consultants in India
Interface: It gives the signature for its memeber like (methods, properties, indexer and events),
It does't allow you to define fields (Ex. int a).
All members in interface are not using any king of access specifier(public, private, protectec, internal etc..).
During implementation the members should be public.
By default all member are virtual so need to use virtual keyword.
Abstract: Class it can contain abstract method(that should be implemented in derived class) and other methods which can use access specifier. It allows to define datatype(ex. int inta). It can't be instantiated
the method which are going to implement those member should use abstract keyword
Abstract Class: A class that cannot be instantiated. An abstract class is a class that must be inherited and have the methods overridden. An abstract class is essentially a blueprint for a class without any implementation.
Interface: Interfaces like classes define a set of properties methods and events. But unlike classes interfaces do not provide implementation. They are implemented by classes and defined as separate entities from classes
Abstract class act like a half defined class
While interface are for standardization and enforcement.
.NET Interview questions
First, no method and property can't implementation in the interface but in abstract class you can implementation such of method or property
Second, interface has any constructor but abstract class can has.
third, you can inherits of some interface but you can inherits of one class or abstract class
Interfaces provide a form of multiple inheritance. A class can extend only one other class. Interfaces are limited to public methods and constants with no implementation. Abstract classes can have a partial implementation, protected parts, static methods, etc. A Class may implement several interfaces. But in case of abstract class, a class may extend only one abstract class. Interfaces are slow as it requires extra indirection to to find corresponding method in in the actual class. Abstract classes are fast.
for .net interview question and answers
pls visit my blog
satyakishore.webs.com
Hi,
Abstract class is the Act sa the base class,It supports implmented methods and unimplimented methods,Abstract calss as followes on derived class.in Abstract class you can Declare the Constructors,fields,methods,indexes,destructors etcExample:pulic Abstract Class A{public void Hi();
public void Hello(){Console.WriteLine("hello method");}
}public Class B{public overid void Hi(){Console.WriteLine("hi method");}}Interface: Interface is the Collection of Abstrcted method is called interface,By default is the Publicin interface you can not Declare the Constructors,fields,methods,indexes,destructors .Examples:'//mutltiple inhiritanceInterface IA{void cat();void Dog();}Interface IB{void door();void tyres();}public class C:IA,IB{public void cat(){Console.WriteLine("hello cat method");}public void dog(){Console.WriteLine("hello dog method");}public void door(){Console.WriteLine("hello door method");}public void tyres(){Console.WriteLine("hello tyres method");}}
Interface are similar to abstraction classes.However , interfaces represent the higest level of abstraction in Object- oriented programming.This is because all the methods in an interface are abstract and do not have implementation.In contrast ,the abstract classes might contain a method that has a body.
89 question on the page
http://www.dotnetquestion.info/dot_net/interview2.htm
Interface only implementaion ,it is fully abstact classes.
Abstract is not implemented class,it is only inherited class
An abstract class may contain complete or incomplete methods. Interfaces can contain only the signature of a method but no body. Thus an abstract class can implement methods but an interface can not implement methods.
· An abstract class can contain fields, constructors, or destructors and implement properties. An interface can not contain fields, constructors, or destructors and it has only the property's signature but no implementation.
· An abstract class cannot support multiple inheritance, but an interface can support multiple inheritance. Thus a class may inherit several interfaces but only one abstract class.
· A class implementing an interface has to implement all the methods of the interface, but the same is not required in the case of an abstract Class.
· Various access modifiers such as abstract, protected, internal, public, virtual, etc. are useful in abstract Classes but not in interfaces.
interface just declaration.it provide standared for programming.it has no code.on the other hand abstaract class is one which can not make object.it is always inherited
such that ie
public abstarct class clscon
{
protected sqlconnection con= new sqlconnection()
public clscon()
con.connectionstring= configurationmanager.connectionstring("cn").connectionstring;
}}//this is abstract class
interface
public interface intemp
get;
set;
}
in interfaces we can only define methods. But we cant implemented those methods in interfaces itself. interfaces allow us to have multiple inheritance.
in abstract classes we can define method and if we want we can implement those methods in abstact class. we cant instantiate from abstract classes.- by Shantha
in abstract classes we can define method and if we want we can implement those methods in abstact class. we cant instantiate from abstract classes.
What is an Interface?An interface is a contract, a specification that concrete classes MUST follow. It defines method signatures but cannot have any implementations; the latter must be provided by the classes that implement the interface.C# differs from C++ in this regard because C++ lacks native language support for interfaces. As a C++ programmers you have to create an interface by defining an abstract class with pure virtual methods.what is an abstract class.................An Abstract class lets you define some behaviors and force your subclasses to provide others. For example, if you have an application framework, an abstract class may provide default services such as event and message handling. Those services allow your application to plug in to your application framework. However, there is some application-specific functionality that only your application can perform. So instead of trying to define these behaviors, the abstract class can declare abstract methods.Differences between Interfaces and Abstract classes Which we use ?I. multiple inheritanceA class may implement several interfaces but can only extend one abstract class.II. default implementationAn interface cannot provide any code at all, much less default code. An abstract class can provide complete code, default code, and/or just stubs that have to be overridden.III. adding functionalityIf you add a new method to an interface, you must track down all implementations of that interface in the universe and provide them with a concrete implementation of that method. If you add a new method to an abstract class, you have the option of providing a default implementation of it. Then all existing code will continue to work without change.IV. is-a vs -able or can-doInterfaces are often used to describe the abilities of a class, not its central identity, e.g. an Automobile class might implement the Recyclable interface, which could apply to many otherwise totally unrelated objects.An abstract class defines the core identity of its descendants.
There are lost of discussion on the internet about the Interface vs Abstract class. Also, as base class whether we have to use interface, abstract class or normal class.
I am trying to point out few considerations on which we can take decision about Interface vs Abstract class vs Class.
Abstract Class vs Interface
I am assuming you are having all the basic knowledge of abstract and interface keyword. I am just briefing the basics.
We can not make instance of Abstract Class as well as Interface.
Here are few differences in Abstract class and Interface as per the definition.
Abstract class can contain abstract methods, abstract property as well as other members (just like normal class).
Interface can only contain abstract methods, properties but we don’t need to put abstract and public keyword. All the methods and properties defined in Interface are by default public and abstract.
//Abstarct Class
public abstract class Vehicles{ private int noOfWheel; private string color; public abstract string Engine { get; set; } public abstract void Accelerator();}
//Interfacepublic interface Vehicles{string Engine { get; set;}void Accelerator();}
We can see abstract class contains private members also we can put some methods with implementation also. But in case of interface only methods and properties allowed.
We use abstract class and Interface for the base class in our application.
This is all about the language definition. Now million dollar question.ThanksManoj(InfoAxon Technology Limited)
In the interface all methods must be abstract, in the abstract class some methods can be concrete. In the interface no accessibility modifiers are allowed, which is ok in abstract classes.