C#. Can I automatically substitute derived class instead of base class

Question

Language is C#.
Say i have overridden method in class A

    class A:B
    {
        protected override void Method(BaseClass bc)
        {
            (DerivedClass)bc.DerivedClassField = blabla;
        }
    }

Is there any library/language feature/etc using which i can write following:

    class A:B
    {
        protected override void Method(BaseClass bc)
        {
            bc.DerivedClassField = blabla;
        }
    }

by, for instance, adding some attribute to class A or something?
Sorry for crappy formatting.

Answer 1

You could use generics to do this in a type-safe way:

class A<T> where T : BaseClass {
    protected virtual void Method(T bc) { ... }
}

class B : A<DerivedClass> {
    protected override void Method(DerivedClass bc) {
        bc.DerivedClassField = blabla;
    }
}

but this might cause other problems if you even want to use A<T> without knowing T, in which case I would use the cast (if the class structure means the cast won't fail) or redefine your object model.