Question

I’ve got a base class, say called Fruits. I then have a few child classes of that, say Banana:Fruit, Apple:Fruit, etc.

I then have a list of objects of different types, Banana, Apple, whatever. That looks like this:

List<Fruits> f = new List<Fruits>{new Banana(), new Banana(), new Apple(), new Banana()};

I want a function that can take a list of fruits as well as a type, and give me a list with only that type’s objects in the list. So if I call find_obj(f, Banana), (or something) it should give me back a list containing only Bananas.

I might be showing extreme ignorance here, and I apologise. Is this even possible? I know I could do something like this if I know the class beforehand:

public List<Fruit> GimmeBanana(List<Fruit> f)
{
     List<Fruit> Output=new List<Fruit>{ };
     foreach(Fruit fr in f)
     {
         if (fr is Banana){ Output.Add(fr); }
     }
}

But I don’t know how to make that work for Any class.

Answer 1

Such a method already exists in the framework – OfType<T>:

List<Banana> bananas = f.OfType<Banana>().ToList();