Method overriding in C sharp

• Method overriding is a feature that allows you to invoke functions (that have the same signatures) that belong to different classes in the same hierarchy of inheritance using the base class reference.
• In other words, it is a concept of having same prototypes (i.e., same function name and same arguments) in the base class and derived class.
• In order to access parent class methods (or fields), base keyword is used.
• C# makes use of two keywords: virtual and overrides to accomplish method overriding.
• Method of the base class must be marked as virtual.
• Method of derived class must be declared as override.
• For e.g.,

• using System;
  
  namespace OverrideDemo
  {
      class BC 
      {
          public virtual int prod(int a, int b)
          {
              return a * b;
          }
      }
  
      class DC1 : BC
      {
          public override int prod(int x, int y)
          {
              int d = 10;
              return base.prod (x, y) * d;
          }
      }
      class DC2 : BC
      {
          public override int prod(int x, int y)
          {
              int d = 20;
              return base.prod(x, y) * d;
          }
      }
      class Demo
      {
          static void Main(string[] args)
          {
              BC obj = new BC();
              Console.WriteLine("From Base class: " + obj.prod(3, 4));
              BC obj1 = new DC1();
              Console.WriteLine("From Derived class 1: " + obj1.prod(3, 4));
              BC obj2 = new DC2();
              Console.WriteLine("From Derived class 2: " + obj2.prod(3, 4)); 
              Console.ReadLine();
          }
      }
  }

Note:

• virtual method must have its implementation in the base class and may optionally be overrided in the derived class if some additional functionality is required
• Signature of the method in base as well as derived class should be the same
• If any class method doesn't have 'virtual', 'abstract' or 'override' keyword and we attempt to have its new implementation in any derived class a warning is generated to supply 'new' keyword to the method in the derived class.We can also not override that class method unless that method has 'virtual' keyword

Question: Can you override private virtual methods?
Answer: No. You cannot access private methods in inherited classes, have to be protected in the base class to allow any sort of access.