Can private class be inherited???

Question

Hi If yes how? Is encapsulation implemented only using modifiers and interface(if i am not wrong)??? What else can be done to implement encapsulation? Thanks

Kavita B · Answer

thanks

Vulpes · Answer

Actually Kavita it struck we later when I was working with some nested classes that we were both wrong - you CAN inherit from a private class! The following compiles and works fine: using System; class A { private class N { public virtual void Hello() { Console.WriteLine(Hello from A.N); } } private class N2 : N { public override void Hello() { Console.WriteLine(Hello from A.N2); } } static void Main() { N n = new N(); n.Hello(); N2 n2 = new N2(); n2.Hello(); Console.ReadKey(); } } However this only works because the derived class N2 is also nested within A and is therefore within the same scope as N. It's difficult to see why anyone would want to do this in practice but it's a good answer to an interview question ;)

Vulpes · Answer

Only nested classes can be private. 'Top level' classes are either internal (by default) or public. So this is OK: class A // internal if no modifier { public int MemberA; // accessible only within current assembly private Class N // not accessible outside A { public int MemberN; // not accessible outside A } } class B : A { // can't access A.N } As Shirsendu said private classes can't be inherited but the enclosing class can be (unless it's sealed). Accessibility to members of a class (strictly speaking a nested class is a static member) is controlled by the access modifier which (in C#) can be public protected internal internal protected or private. If you don't use a modifier then a member is private by default. However a member's accessibility may be limited by the accessibility of the class itself because a member cannot be more accessible than its class. So for example if you declare public members of an internal class then those members will also effectively be internal. Similarly if you declare public members of a private class then those members (like the nested class itself) will not be accessible outside the enclosing class. If a class implements an interface then all the implemented members must be declared public. The only exception to this is where a member is implemented explicitly: IFace { void MethodI(); // access modifier not allowed but implicitly public void MethodE(); // ditto } class C : IFace { public void MethodI(){} // public needed here void IFace.MethodE(){} // implemented explicitly so no access modifier allowed } The only way to access IFace.MethodE is through an IFace reference: C c = new C(); c.MethodI(); // OK c.MethodE(); // not allowed ((IFace)c).MethodE(); // OK So in a sense IFace.MethodE() is both public and private :)

Shirsendu Nandi · Answer

No Private class vannot be inherited.