How can you use optional parameters in C#?

Question

^{Note: This question was asked at a time when C# did not yet support optional parameters (i.e. before C# 4).}

We\'re building a web API tha

Answer 1

Hello Optional World

If you want the runtime to supply a default parameter value, you have to use reflection to make the call. Not as nice as the other suggestions for this question, but compatible with VB.NET.

using System;
using System.Runtime.InteropServices;
using System.Reflection;

namespace ConsoleApplication1
{
    class Class1
    {
        public static void sayHelloTo(
            [Optional,
            DefaultParameterValue("world")] string whom)
        {
            Console.WriteLine("Hello " + whom);
        }

        [STAThread]
        static void Main(string[] args)
        {
            MethodInfo mi = typeof(Class1).GetMethod("sayHelloTo");
            mi.Invoke(null, new Object[] { Missing.Value });
        }
    }
}