Abstract Classes and Methods in OOP C#

Abstract Classes:

Abstract class is a class that can contain abstract methods, It can be inherited by another abstract classes, you can not create its instance because it may contain Abstract (unimplemented) Methods. If a class consist any abstract method than that call must also be an abstract class. Example:

abstract class Human

{

    //Any valid code goes here

}

class Program

{

    static void Main(string[] args)

    {

        Human h;

        //Error: Cannot create the instance of abstract class       

        h = new Human();       

    }

}

Abstract Functions:

Abstract Methods or Functions are the unimplemented methods that does not contain body. They must be implemented(overridden) in a child class. You can not declare static methods as abstract, override or virtual. Example:

abstract class Human

{

    protected string name;

    public abstract void Display();// abstract methods

  public void anotherMethod()// may contain implemented methods

    {

        Console.WriteLine("anotherMethod() ...");

    }

}

class Student:Human

{

    protected int regNo;

    public override void Display()// abstract classes must be overridden 

    {

        Console.WriteLine("{0} {1}", name, regNo);

    }

}

Thanks to msdn.microsoft.com for knowledge and examples

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