using System;
using System.Runtime.Serialization;

namespace ConsoleApplication1
{
    class A
    {
        public A(string param)
        {
            Console.WriteLine(param);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var a = (A)FormatterServices.GetUninitializedObject(typeof(A));
            var ctor = typeof(A).GetConstructor(new[] { typeof(string) });
            ctor.Invoke(a, new[] { "123" });
        }
    }
}