C# Factory Pattern - Base method will always get called

Question

I'm wondering why in the following example does the base method always get called even though I'm overriding it when the Factory Pattern "Builder" returns a new instance of the object?

interface FactoryInter 
{
    void MakeDetails();

}

class Builder {

    public static Builder getObject(string obj)
    {
        if(obj == "Cont")
        {
            return new Cont();
        }else{
            return new Builder();
        }

    }

    public void MakeDetails()
    {
        Console.WriteLine("I will always get called..");
    }

}

class Cont : Builder, FactoryInter {

    public void MakeDetails()
    {
        Console.WriteLine("Hello..");
    }

}

public class Test
{
    public static void Main()
    {
        Builder b = new Builder();
        b = Builder.getObject("Cont");

        b.MakeDetails();
        // your code goes here
    }
}

Any help would be greatly appreciated

See http://stackoverflow.com/questions/814934/why-c-sharp-implements-methods-as-non-virtual-by-default — Kirk Woll, Jul 25 '14 at 14:19

Savvas Kleanthous · Answer 1 · 2014-07-25T14:21:28.827

You do not override it. You are hiding it. Method Cont.MakeDetails() is hiding the base class's MakeDetails method. For more details please see the below example:

class Base
{
    public void Hidden()
    {
        Console.WriteLine("Base!");
    }

    public virtual void Overrideable()
    {
        Console.WriteLine("Overridable BASE.");
    }
}

class Derived : Base
{
    public void Hidden()
    {
        Console.WriteLine("Derived");
    }

    public override void Overrideable()
    {
        Console.WriteLine("Overrideable DERIVED");
    }
}

Now testing them yields these results:

var bas = new Base();
var der = new Derived();

bas.Hidden(); //This outputs Base!
der.Hidden(); //This outputs Derived
((Base)der).Hidden(); 
//The above outputs Base! because you are essentially referencing the hidden method!

//Both the below output Overrideable DERIVED 
der.Overrideable();
((Base)der).Overrideable();

To override it, mark the base method as virtual and the derived one as override.

SKleanthous has it spot on. A more detailed explanation can be found [here](http://msdn.microsoft.com/en-us/library/ms173153.aspx) — Gridly, Jul 25 '14 at 14:39

C# Factory Pattern - Base method will always get called

1 Answers1