IDictionary<,> contravariance?

Question

I have the following method in an external class

public static void DoStuffWithAnimals(IDictionary animals)

In my cal

Answer 1

Solution wise you could do something like this, just pass in an accessor instead:

    public static void DoStuffWithAnimals(Func getAnimal)
    {
    }

    var dicLions = new Dictionary();
    DoStuffWithAnimals(s => dicLions[s]);

Obviously that is likely to be a bit simple for your needs, but if you only need a couple of the dictionary methods it's pretty easy to get that in place.

This is another way that gives you a bit of code re-use between your animals:

    public class Accessor : IAnimalAccessor where T : Animal
    {
        private readonly Dictionary _dict;

        public Accessor(Dictionary dict)
        {
            _dict = dict;
        }

        public Animal GetItem(String key)
        {
            return _dict[key];
        }
    }

    public interface IAnimalAccessor
    {
        Animal GetItem(string key);
    }

    public static void DoStuffWithAnimals(IAnimalAccessor getAnimal)
    {
    }

    var dicLions = new Dictionary();
    var accessor = new Accessor(dicLions);
    DoStuffWithAnimals(accessor);