using System;

   public class Sample {

        public static int a=10,b=15;

        private Sample()

        {  

        }

​

        public static int sum()

        {

            return a + b;

        }

    }

​

    public class PrivateConstructorProgram {

        public  static void Main(string[] args)

        {

            // calling the private constructor using class name directly 

            int result = Sample.sum();

            Console.WriteLine(result);

            // Below code will throw the error as we can't create object of this class

            // Sample objClass = new Sample(); 

        }

    }

​