Compiler says I am not implementing my interface, but I am?

Question

Okay, I have two namespaces. One contains my interface and one contains the implementing class. Like this:

namespace Project.DataAccess.Interfaces
{
    public i         


        

Answer 1

You have 2 basic options when implementing intefaces: implicit or explicit. Implicit implementation takes on the form of a public method or property, while explicit is in the form of a method or property prefaced with the IFoo. modifier that is otherwise not public.

interface IFoo
{
    void Bar();
}

class FooA : IFoo
{
    public void Bar() { }
}

class FooB : IFoo
{
    void IFoo.Bar() { }
}

The difference here is that in the case of FooA, void Bar is part of the publicly visible API of the class. Code can call Bar via the instance of the class.

FooA foo = new FooA(); 
foo.Bar(); // legal

In the case of FooB, void Bar is not part of the publicly visible API of the class. The method can still be called, but it must explicitly be called via the interface.

FooB foo = new FooB();
foo.Bar(); // not legal
IFoo myFoo = foo;
myFoo.Bar(); // legal

Your code does not compile because it walks in the uncharted waters between an implicit and explicit interface implementation. You saw that with your change, you had legally defined an explicit implementation, which is why that particular version compiles. Otherwise, you've also found that the public modifer is needed to make the non-explicit version compile.