In C#, all constructors in polymorphism will fire, starting at the top of the tree and working down. Sometimes this isn't the desired behavior. Here's a potential workaround using a simple Window Console application.

gistfile1.cs

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            B myObj = new B();
            // comment the next line to disable parent constructor
            myObj.Initialize();
        }
    }
    class A
    {
        public A()
        {
            Type t =this.GetType();
            if (t == typeof(A))
            {
                /* Notice that our constructor merely invokes a method.
                 * This ensures that no code is limited to instantiation.
                 */
                this.Initialize();
            }
        }
        public void Initialize()
        {
            /* Here's where the real "constructing" happens. Since it's
             * a regular method, we can call it any time we want - we're
             * not dependent on instantiation.
             */
            Console.WriteLine("A");
        }
    }

    class B : A
    {
        public B()
        {
            Console.WriteLine("B");
        }
    }
}