using System;

​

public class Program

{

    public static void Main()

    {

        // TestMethod called without the second parameter

        TestMethod(5);

    }

    // TestMethod has an optional parameter called 'optionalNumber'

    // optional parameters must be the last parameters in the signature and have a default value supplied

    static void TestMethod(int notOptionalNumber, int optionalNumber = 10)

    {

        Console.Write(optionalNumber + notOptionalNumber);

    }

}