Abstract Class in .Net

Defination:-  

 abstract class is a special class which have no any object .it only allows other classes to inherit from it.

An abstract class can contain either abstract methods or non abstract methods. Abstract members do not have any implementation in the abstract class, but the same has to be provided in its derived class.

Example :

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication2
{

abstract class Class1
{
public void Add(int n1, int n2)
{
int n3;
n3= n1 + n2;
Console.WriteLine("N3:" + n3);
Console.ReadLine();
}
public abstract void Multiply(int x, int y);

}


class Program:Class1
{
string c;
int z;
public void Concatenate(string a, string b)
{
c = a + b;
Console.WriteLine(" C:" + c);
Console.ReadLine();
}
public static void Main(string[] args)
{
Program pgm = new Program();
pgm.Add(10, 20);
pgm.Concatenate("Hem", "nath");
pgm.Multiply(20, 100);

}
public override void Multiply(int e, int f)
{
z = e * f;
Console.WriteLine("Z:" + z);
Console.ReadLine();
}
}

}

In the above sample, you can see that the abstract class Class1 contains two methods Add and Multiply. Add is a non-abstract method which contains implementation and Multiply is an abstract method that does not contain implementation.
The class Program is derived from Class1 and the Multiply is implemented on Program. Within the Main, an instance ( pgm) of the Program is created, and calls Add and Multiply.