What is late binding in C#?

In static polymorphism, the response to a function is determined at the compile time. In dynamic polymorphism, it is decided at run-time. Dynamic polymorphism is what we call late binding.

Dynamic polymorphism is implemented by abstract classes and virtual functions. The following is an example showing an example of dynamic polymorphism −

Example

 Live Demo

using System;

namespace PolymorphismApplication {
   class Shape {
      protected int width, height;

      public Shape( int a = 0, int b = 0) {
         width = a;
         height = b;
      }

      public virtual int area() {
         Console.WriteLine("Parent class area :");
         return 0;
      }
   }

   class Rectangle: Shape {
      public Rectangle( int a = 0, int b = 0): base(a, b) {}
      public override int area () {
         Console.WriteLine("Rectangle class area :");
         return (width * height);
      }
   }

   class Triangle: Shape {
      public Triangle(int a = 0, int b = 0): base(a, b) {}
      public override int area() {
         Console.WriteLine("Triangle class area :");
         return (width * height / 2);
      }
   }

   class Caller {
      public void CallArea(Shape sh) {
         int a;
         a = sh.area();
         Console.WriteLine("Area: {0}", a);
      }
   }

   class Tester {
      static void Main(string[] args) {
         Caller c = new Caller();
         Rectangle r = new Rectangle(10, 7);
         Triangle t = new Triangle(10, 5);
         c.CallArea(r);
         c.CallArea(t);
         Console.ReadKey();
      }
   }
}

Output

Rectangle class area :
Area: 70
Triangle class area :
Area: 25