IDictionary<,> contravariance?

Question

I have the following method in an external class

public static void DoStuffWithAnimals(IDictionary animals)

In my cal

Answer 1

You could modify public static void DoStuffWithAnimals(IDictionary animals) to add a generic constraint. Here is something that works for me in LINQPad:

void Main()
{
    var lions = new Dictionary();
    lions.Add("one", new Lion{Name="Ben"});
    AnimalManipulator.DoStuffWithAnimals(lions);
}

public class AnimalManipulator
{
    public static void DoStuffWithAnimals(IDictionary animals)
    where T : Animal
    {
        foreach (var kvp in animals)
        {
            kvp.Value.MakeNoise();
        }
    }
}

public class Animal
{
    public string Name {get;set;}
    public virtual string MakeNoise()
    {
        return "?";
    }
}

public class Lion : Animal
{
    public override string MakeNoise()
    {
        return "Roar";
    }
}