Explicit C# interface implementation of interfaces

Question

Consider the following three interfaces:

interface IBaseInterface
{
    event EventHandler SomeEvent;
}

interface IInterface1 : IBaseInterface
{
    ...
}

interface IInterface2 : IBaseInterface
{
    ...
}

Now consider the following class that implements both IInterface1 and IInterface 2:

class Foo : IInterface1, IInterface2
{
    event EventHandler IInterface1.SomeEvent
    {
        add { ... }
        remove { ... }
    }

    event EventHandler IInterface2.SomeEvent
    {
        add { ... }
        remove { ... }
    }
}

This results in an error because SomeEvent is not part of IInterface1 or IInterface2, it is part of IBaseInterface.

How can the class Foo implement both IInterface1 and IInterface2?

Answer 1

You can use generics:

interface IBaseInterface<T> where T : IBaseInterface<T>
{
    event EventHandler SomeEvent;
}

interface IInterface1 : IBaseInterface<IInterface1>
{
    ...
}

interface IInterface2 : IBaseInterface<IInterface2>
{
    ...
}

class Foo : IInterface1, IInterface2
{
    event EventHandler IBaseInterface<IInterface1>.SomeEvent
    {
        add { ... }
        remove { ... }
    }

    event EventHandler IBaseInterface<IInterface2>.SomeEvent
    {
        add { ... }
        remove { ... }
    }
}    

Answer 2

interface IBaseInterface
{
    event EventHandler SomeEvent;
}

interface IInterface1 : IBaseInterface
{
    event EventHandler SomeEvent;
}

interface IInterface2 : IBaseInterface
{
    event EventHandler SomeEvent;
}

class Foo : IInterface1, IInterface2
{

    public event EventHandler SomeEvent
    {
        add { }
        remove { }
    }

    event EventHandler IInterface1.SomeEvent
    {
        add { }
        remove { }
    }


    event EventHandler IInterface2.SomeEvent
    {
        add { }
        remove { }
    }
}  

Answer 3

SomeEvent isn't part of IInterface1 or IInterface2, its a part of IBaseInterface.

class Foo : IInterface1, IInterface2
{
    event EventHandler IBaseInterface.SomeEvent {
        add { ... }
        remove { ... }
    }
}