Program in C# to demonstrate abstract class and abstract methods.

using System;
abstract class Test {
public int a;
public abstract void A();
}
class Derived1:Test {
public override void A() {
Console.WriteLine(“Derived1 A”);
base.a++;
Console.WriteLine(“a = {0}”,base.a);
}
}
class Derived2:Test {
public override void A() {
Console.WriteLine(“Derived2 A”);
base.a–;
Console.WriteLine(“a = {0}”,base.a);
}
}
class ProgramApp {
static void Main(String[] args) {
Test test1=new Derived1();
test1.A();
Test test2=new Derived2();
test2.A();
}
}