Reversed order of constructor calls by inheriting a constructor

Question

I have a class that first needs to call the derived class constructor before it calls the base constructor. I know that by the following code the base constructor will be called first

public class A {

    protected A () {
        //do something
    }

}

public class B : A {

    public B () : base() {
        //do something else
    }

}

Is their a way to reverse that order, or a work around for it. The solution with creating an additional protected method in the base-class like doConstructor() and call it in the derived constructor after the first task isn't possible with readonly fields because the compiler will not accept it.

Answer 1

There's no direct way to accomplish this. In the past, I've encountered this situation too and used an Initialize method to work around it.

public class A
{
    protected A()
    {
        // Do pre-initialization here still.

        Initialize();
    }

    protected virtual Initialize()
    {
        // Do all post-derived-class initialization here.
    }
}

public class B : A
{
    public B()
        : base()
    {
    }

    protected override Initialize()
    {
        // Do initialization between pre- and post- initialization here.

        base.Initialize();
    }
}

As long as you follow the guidelines of pre-, post-, and normal initialization here, it could be reasonably safe and within good practice.