extension methods, C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            C ob= new C();
        }
    }
    
    public class A
    {
        public void name()
        {
          Console.WriteLine("Rajesh Patnaik");
        }
        
        public void address()
        {
          Console.WriteLine("Wipro");
        }
        
    }
    
    public static class B
    {
        public static void contactaddress(this A obj)
        {
           Console.WriteLine("Marathalli");
        }
        
    }
    
    class C
    {
        A ob = new A();
        public C()
        {
            ob.name();
            ob.address();
            ob.contactaddress();
        }
        
    }
        
}

Show compiler warnings [ + ] Show input
Compilation time: 0,17 sec, absolute running time: 0,11 sec, cpu time: 0,12 sec, average memory usage: 16 Mb, average nr of threads: 3, absolute service time: 0,32 sec