Question

The follow is bad code. Please help me achieve what I’m trying to achieve, but with good code.
I want to have an object array that is derived from a base. I want to be able to use that array in BaseClass when DoStuff() runs. I know that I cannot downcast, that’s not what i’m looking to do here. I just want to be able to set Fields in the derived class, and use Fields in the base DoStuff().

public class BaseObject
{

}

public class DerivedObject : BaseObject
{

}

public class BaseClass
{
    public BaseObject[] Objects;

    public virtual void DoStuff()
    {
        // use the Objects
    }
}

public class DerivedClass : BaseClass
{
    public override DerivedObject[] Objects;

    public override void DoStuff()
    {
        // Do stuff unique to the derived.

        base.DoStuff();
    }
}

Answer 1

You are looking for generics?

public class BaseClass<T>
where T : BaseObject
{
    public T[] Objects;

    public virtual void DoStuff()
    {
        // use the Objects
    }
}

public class DerivedClass : BaseClass<DerivedObject>
{
    public override void DoStuff()
    {
        // Do stuff unique to the derived.

        base.DoStuff();
    }
}

In the above code field of T type (generic or parameter type) is declared, T is constrained to be BaseObject or class inherited from BaseObject, when DerivedClass is declared DerivedObject is specified in place of T, so in DerivedClass Objects field can be used as DerivedObject[].