static void Main(string[] args) { NumberManipulator n = new NumberManipulator(); /* local variable definition */ int a = 100; int b = 200; Console.WriteLine("Before swap, value of a : {0}", a); Console.WriteLine("Before swap, value of b : {0}", b); /* calling a function to swap the values */ n.swap(a, b); Console.WriteLine("After swap, value of a : {0}", a); Console.WriteLine("After swap, value of b : {0}", b); n.swap_ref(ref a, ref b); Console.WriteLine("This is the reference swap"); Console.WriteLine("After swap, value of a : {0}", a); Console.WriteLine("After swap, value of b : {0}", b); Console.ReadLine(); }