Why can’t we specify the accessibility modifier for methods inside the interface ?

Question

Why can't we specify the accessibility modifier for methods inside the interface ?

Andrew Fenster · Answer

The entire purpose of an interface is to declare a list of public methods that can be accessed by other classes . If you had private methods, other classes wouldn't be able to access them. If you want to specify private or protected methods, you need to create a base class instead. Honestly, this is a very important topic for you to understand. If you want to make your living as a programmer, it's something you absolutely must master. You should get a book and spend several hours studying the subject. Then go over it again next week and again next month and again the month after that, etc. You can't get it by asking questions on a forum.

Vulpes · Answer

As Krishna said, members of interfaces are always implicitly public which is why access modifiers are not needed (and indeed not allowed) in the interface itself. However, when you implement the interface, you do have to use the public access modifier unless you are implementing a member explicitly. For example: interface IFace { void Method1(); void Method2(); } class MyClass : IFace { public void Method1(){ // code } void IFace.Method2() { // code } // implemented explicitly so no public } Notice also that Method2 can only be called via an IFace reference: MyClass mc = new MyClass(); mc.Method1(); mc.Method2(); // not allowed ((IFace)mc).Method2(); // fine

Krishna Garad · Answer

First thing is that Interface is nothing but the set of rules and interface and it's members are always public. Think if we are creating some rule for our team development means it is not applicable to some members. This rules are applicable who implement that interface but who don't want to implement that interface they want to free life they are free from this. Interface is only set of rule if we are applying any accessibility on the rules then why to implement the interface. Who want the restriction on there own they may implement that interface and who dont want they will not implement that interface. That's the reason we can't specify accessibility modifier for methods or any other member of inside the interface. Interface contain only decleration not Defination. Whatever defenation we are giving that in the classes who are implement that interface.