C# - Inheritance and interfaces

Question

Sorry for the bad title, but I didn't know how to entitle this in a good way.

Let the following interfaces :

interface IFoo
{
}

interface IBar
{
}

And the following classes :

class Base
{
}

class Derived1 : Base, IFoo, IBar
{
}

class Derived2 : Base, IFoo, IBar
{
}

I need to have a common type for Derived1 and Derived2 that has all the features of Base, IFoo and IBar. so that i can have instances of both Derived1 and Derived2 into the same collection and have access to the features of Base, IFoo and IBar without doing some reflexion black magic.

If Base was an interface, I would just have to create an interface requiring to implement Base, IFoo and IBar, but it's not the case.

I also do not want to have an intermediate inheritance between Derived1 / Derived2 and Base :

class Intermediate : Base, IFoo, IBar
{
}

class Derived1 : Intermediate
{
}

class Derived2 : Intermediate
{
}

Because I'm in the context of Unity and inheritance is to be avoided there more than anywhere.

Also I cannot modify Base.

I thought about having an IBase interface that requires all the features of Base and have an "intermediate" interface requiring to implement it too, i.e :

interface IIntermediate : IBase, IFoo, IBar
{
}

class Derived1 : Base, IIntermediate
{
}

class Derived2 : Base, IIntermediate
{
}

But I would have to copy all of the features of Base (and its parents) into IBase and IBase would also not be a Base. So that looks a bit dirty and might cause me problems I don't see yet.

I there a different way to acheive what I need to do other than the two possibilities mentionned above ? Thank you !

Answer 1

How about a class with implicit operators to be able to get constructed and return all the desired types.

class MyBase : IFoo, IBar
{
    Base innerValue;
    public static implicit operator Base(MyBase value)
    {
        return value.innerValue;
    }

    public static implicit operator MyBase(Derived1 value)
    {
        return new MyBase(value);
    }

    public static implicit operator MyBase(Derived2 value)
    {
        return new MyBase(value);
    }

    public MyBase(Derived1 value)
    {
        innerValue = value;
    }
    public MyBase(Derived2 value)
    {
        innerValue = value;
    }
    // Implement IFoo and IBar based on innerValue calls
}

This would allow you to create an array like this:

MyBase[] myArray = new MyBase[] {new Derived1(), new Derived2()};

And you could still treat each instance as a Base:

Base B1 = myArray[0];