Call the base method automatically

Question

I need to call a base class method when you call overriden one (e.g. callor base). For instance:

class A { public void Fun() { Console.Write("Class A!"); } } class B : A { public void Fun() { Console.Write("Class B!"); } } 

I want to see on the screen

Class A! Class B!

when executing the following code:

 B b = new B(); b.Fun(); 

Can someone tell me, please, what needs to be changed in the code example or what is the best way to write in order to get the required result? Thanks.

Answer 1

If you do not want to explicitly call it, and therefore call A.Fun() in a derived class, you can use something called a template template template :

 class A { public void Fun() { Console.Write("Class A!"); FunProtected(); } protected virtual void FunProtected() { } } class B : A { protected override void FunProtected() { Console.Write("Class B!"); } } 

This will give you:

 new A().Fun() -> "Class A!" new B().Fun() -> "Class A! Class B!" 

Answer 2

If you need this behavior, you will need to change the platform / language..NET does not automatically call the base method. You must call this explicitly. Also, your method must be virtual or you will hide it in a derived class:

 class A { public virtual void Fun() { Console.Write("Class A!"); } } class B : A { public override void Fun() { // call the base method which will print Class A! base.Fun(); Console.Write("Class B!"); } } 

Now that you do this:

 B b = new B(); b.Fun(); 

You will get the desired result.

Answer 3

Maybe so:

 interface IFun { void Fun(); } abstract class A : IFun { void IFun.Fun() { Console.Write("Class A!"); Fun(); } protected abstract void Fun(); } class B : A { protected override void Fun() { Console.Write("Class B!"); } } IFun b = new B(); b.Fun(); 

This works if the object reference is IFun.

Answer 4

Just for reference, you can use a wrapper template that places A inside B. Here's a rough example!

 interface IFunClass { void Fun(); } class A : IFunClass { public void IFunClass.Fun() { Console.Write("Class A!"); } } class B : IFunClass { public B(IFunClass f) { this.m_SomethingFun = f; } public void IFunClass.Fun() { this.m_SomethingFun.Fun(); Console.Write("Class B!"); } private IFunClass m_SomethingFun; } A a = new A(); B b = new B(a); b.Fun() // will call a.Fun() first inside b.Fun()