From base class in C#, get derived type?

core picture core · Jun 9, 2009 · Viewed 49k times · Source

Let's say we've got these two classes:

public class Derived : Base
{
    public Derived(string s)
        : base(s)
    { }
}

public class Base
{
    protected Base(string s)
    {

    }
}

How can I find out from within the constructor of Base that Derived is the invoker? This is what I came up with:

public class Derived : Base
{
    public Derived(string s)
        : base(typeof(Derived), s)
    { }
}

public class Base
{
    protected Base(Type type, string s)
    {

    }
}

Is there another way that doesn't require passing typeof(Derived), for example, some way of using reflection from within Base's constructor?

Answer

Juliet picture Juliet · Jun 9, 2009
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