Inheritance

sunsher

Hi, I have a class A that inherits another class B and calls a method in Class B. That method in turn calls another method which is overridable in Class B. Now, I want the inner method to be created in the calling Class A. But I noticed that the control comes to the first method in Class B and then goes to the inner method in Class B itself. Is it possible to bypass that inner method and call my overrided method instead? Thanks

PIEBALDconsult

Can you show the minimum amount of code required to demonstrate the situation?

BillWoodruff

The least you can do is show the code you are working with, and make some effort. Look up the words 'new and 'override in the context of .NET inheritance, think about them, try using them, then, come back here with specific questions and code.

«There is a spectrum, from "clearly desirable behaviour," to "possibly dodgy behavior that still makes some sense," to "clearly undesirable behavior." We try to make the latter into warnings or, better, errors. But stuff that is in the middle category you don’t want to restrict unless there is a clear way to work around it.» Eric Lippert, May 14, 2008

Rob Philpott

That's a confusing sentence, but make sure the methods in the base class are marked as virtual.

Regards, Rob Philpott.

OriginalGriff

Yes - that is exactly what inheritance and method overriding is all about!

public class A : B
{
public void DoIt()
{
Console.WriteLine("A:DoIt");
InB();
}
public override void Inner()
{
base.Inner();
Console.WriteLine("A:Inner");
}
}
public class B
{
public void InB()
{
Console.WriteLine("B:InB");
Inner();
}
public virtual void Inner()
{
Console.WriteLine("B:Innner");
}
}

Then when you create an instance:

        A a = new A();
        a.DoIt();

You get:

A:DoIt
B:InB
B:Innner
A:Inner

Because B.Inner is marked as virtual it can be overridden in derived classed - as it is in A - and the system will look for the most "appropriate" version to call. Because a is declared as an instance of the A class, it calls the A version of the method. If you declared a as a B instead but assigned it an A (which is perfectly fine as every A is a "superset" of B):

        B b = new A();
        b.Inner();

You can't call the DoIt method (because B doesn't contain a definition for DoIt), but you will still get:

B:Innner
A:Inner

Becuase the value inside the variable b is still an instance of the A class so the system calls the "latest" version.

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sunsher

Thanks all for your help. I now have an insight on Inheritance. :)

OriginalGriff

You're welcome!

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