Decorating a class with protected methods

Question

I want to do the exactly the same thing described here, but in C#.

public interface IFoo { void DoSomething(); }

public class Foo : IFoo
{
    public void DoSomething() {...}
    protected void Bar() {...}
}

public class Foo2 : IFoo
{
    private readonly Foo _foo;

    public Foo2 (Foo foo) { _foo = foo; }

    public void DoSomething() {...}

    protected void Bar()
    {
        _foo.Bar(); // cannot access Bar() from here
    }
}

I looked at several similar questions, but none of them really tell you exactly how to solve this problem. Is trying to decorate a class with protected method a wrong thing to do in the first place?

The entire idea about `protected` is that it is only accessible in the current class and its subclasses. You will never be able to access it in a class that just holds a reference to it, both in Java and C#. — Jeroen Vannevel, Feb 08 '14 at 15:57

score 5 · Accepted Answer · answered Feb 08 '14 at 15:57

5

Protected methods are only visible to subclasses. If Foo and Foo2 are in the same assembly you can make Foo.Bar internal instead:

public class Foo
{
    internal void Bar() { ... }
}

answered Feb 08 '14 at 15:57

Lee

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Thanks, this seems like a reasonable approach. – CookieEater Feb 08 '14 at 16:25

score 0 · Answer 2 · edited May 23 '17 at 11:52

0

The only difference is that protected methods can be used in derived classes and private methods cannot. So it's not a matter of right or wrong, but rather it's a matter of whether or not you need that functionality.

See this SO answer for more clarification.

edited May 23 '17 at 11:52

Community

1
1

answered Feb 08 '14 at 15:57

Code Maverick

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neodim · Answer 3 · 2014-02-08T16:23:16.963

0

You may make intermediate class FooInternal:

public interface IFoo { void DoSomething(); }

public class Foo : IFoo
{
    public void DoSomething() {}
    protected void Bar() {}
}

public class FooInternal : Foo
{
    internal void Bar()
    {
        base.Bar();
    }
}

public class Foo2 : IFoo
{
    private readonly FooInternal _foo;

    public Foo2(FooInternal foo) { _foo = foo; }

    public void DoSomething() {}

    protected void Bar()
    {
        _foo.Bar(); // can access Bar() from here
    }
}

edited Feb 08 '14 at 16:23

answered Feb 08 '14 at 16:11

neodim

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4
15

But you are making Bar as a public method there. – CookieEater Feb 08 '14 at 16:15
By @Lee advice you may make this method internal. I have updated my answer. – neodim Feb 08 '14 at 16:22

Decorating a class with protected methods

3 Answers3