Is there a way to automatically call a particular method immediately after all constructors have run?

Question

I want to be able to call a particular method automatically upon construction of a derived object, however I can\'t think how to do it. The following code illustrates. Another a

Answer 1

While @Jeremy Todd's (accepted) answer works and is a widely accepted solution to the problem, it has a drawback: not very IoC and serialization friendly, since your class cannot be properly constructed using new. Let me introduce a general solution using some C# features. Note that this solution does not require you to use a factory pattern or invoke anything after constructing the object, and it works on any class with just implementing an interface with a single method. First we declare an interface that our classes will have to implement:

public interface IInitialize {
    void OnInitialize();
}

Next we add a static extension class for this interface, and add the Initialize method:

public static class InitializeExtensions
{
    public static void Initialize(this T obj) where T: IInitialize
    {
        if (obj.GetType() == typeof(T))    
            obj.OnInitialize();
    }
}

Now, if we need a class and all of its descendants to call an initializer right after the object is fully constructed, all we need to do is implement IInitialize and append a line in the constructor:

public class Parent : IInitialize
{
    public virtual void OnInitialize()
    {
        Console.WriteLine("Parent");
    }

    public Parent()
    {
        this.Initialize();
    }
}

public class Child : Parent
{
    public Child()
    {
        this.Initialize();
    }

    public override void OnInitialize()
    {
        Console.WriteLine("Child");
    }
}

public class GrandChild : Child
{
    public GrandChild()
    {
        this.Initialize();
    }

    public override void OnInitialize()
    {
        Console.WriteLine("GrandChild");
    }
}

The trick is that when a derived class calls the extension method Initialize, that will suppress any calls not made from the actual class.