using System;

using System.Reflection;

using System.Globalization;

​

​

public class Foo

{

    public Foo(string a = null, string b = null)

    {

      Console.WriteLine("Foo called with a = " + (a ?? "<null>") + " and b = " + (b ?? "<null>"));

    }

}

​

public class Program

{

    public static void Main()

    {

        var bf = BindingFlags.CreateInstance | BindingFlags.Public | BindingFlags.Instance | BindingFlags.OptionalParamBinding;

        Activator.CreateInstance(typeof(Foo), bf, null, new object [] { }, CultureInfo.CurrentCulture);

        Activator.CreateInstance(typeof(Foo), bf, null, new object [] { "Foo" }, CultureInfo.CurrentCulture);

        Activator.CreateInstance(typeof(Foo), bf, null, new object [] { "Foo", "Bar" }, CultureInfo.CurrentCulture);

    }

}