From base class in C#, get derived type?

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Base b = new Base();
            Derived1 d1 = new Derived1();
            Derived2 d2 = new Derived2();
            Base d3 = new Derived1();
            Base d4 = new Derived2();
            Console.ReadKey(true);
        }
    }

    class Base
    {
        public Base()
        {
            Console.WriteLine("Base Constructor. Calling type: {0}", this.GetType().Name);
        }
    }

    class Derived1 : Base { }
    class Derived2 : Base { }
}

This program outputs the following:

Base Constructor: Calling type: Base
Base Constructor: Calling type: Derived1
Base Constructor: Calling type: Derived2
Base Constructor: Calling type: Derived1
Base Constructor: Calling type: Derived2