CODEWITHSUNDEEP
c#oopinheritance
Manish Kumar
Manish Kumar

Reputation: 343

Protected method not appear in Inheritance

Why does the protected method not appear? If I make any public, internal or protected internal method they get appear.

class A
{
    protected void AProtected() { }
}

class B:A
{
    protected void BProtected() { }
}

class C:B
{
    protected void CProtected() { }
}

class D:C
{
    protected void DProtected() { }
}

class Program
{
    static void Main(string[] args)
    {
        D classD = new D();
        classD.               //no method appear.
    }
}

Upvotes: 0

Views: 1218

Answers (6)

hngr18
hngr18

Reputation: 857

Another one to watch out for is if the method in the derived class is static. You can't call instance methods from a static method in a derived class, regardless of visibility/access modifiers.

If you have 

namespace A
{
    public class AClass
    {
        public void MethodCall()
        {
            xxx
        }
    }
}

Works

namespace B
{
    public class BClass : A.AClass
    {
        public void Go()
        {
            A.AClass.MethodCall();
        }
    }
}

Doesn't Work

namespace B
{
    public class BClass : A.AClass
    {
        public **static** void Go()
        {
            A.AClass.MethodCall();
        }
    }
}

Upvotes: 0

Jeroen Vannevel
Jeroen Vannevel

Reputation: 44439

Because protected methods are accessible to the current class and subclasses of that class. Program is not a subclass of D.

Documentation

A protected member is accessible within its class and by derived class instances.

Accessibility levels

enter image description here

Since I notice confusion: you can call those protected methods from inside the subclass but you cannot call them from outside the subclass onto that subclass.

This might illustrate it:

Create two classes that don't have anything to do with eachother

MyMethod is NOT accessible

enter image description here

Add inheritance between these two classes

MyMethod IS accessible from the subclass

enter image description here

Try to call the method from another class

MyMethod is NOT accessible

enter image description here

Upvotes: 4

Dmitrii Bychenko
Dmitrii Bychenko

Reputation: 186668

Protected methods can be called within derived classes only:

class A {
  // This method can be called within derived classes only
  protected void ProtectedA() {...}
  // This method can be called within classes that are in the same namespace
  internal void InternalA() {...} 
  // This method can be called either within derived classes only or
  // within classes that are in the same namespace
  protected internal void InternalOrProtectedA() {...} 
}

class B: A {
  protected void ProtectedB() {
    // You can call A.ProtectedA() here since B is derived from A
  }
}

class Program {
  static void Main(string[] args)
    // You can NOT call A.ProtectedA() here since B is NOT derived from A
    // But you can call
    //   A.InternalA() since classes Program and A are in the same namespace
    //   A.InternalOrProtectedA() on the same reason
  }
}

Upvotes: 0

Wouter de Kort
Wouter de Kort

Reputation: 39888

Because that's the whole idea of protected. Protected members are only accessible by the declaring class and other classes that inherit from it.

You can find the official documentation here.

Upvotes: 1

yoozer8
yoozer8

Reputation: 7489

Protected is similar to private in that in can only be accessed from within the class, but has the added benefit of being accessible from inherited classes.

Your class Program (and its main method) are not able to access private or protected methods of your other classes, only public.

Upvotes: 0

Sven Grosen
Sven Grosen

Reputation: 5636

Because protected methods are not visible outside of the class or a class that inherits from that class.

From MSDN:

The protected keyword is a member access modifier. A protected member is accessible within its class and by derived class instances.

You could call DProtected() within D, but not outside of D.

Upvotes: 0

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