covariance.cs

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
        }
    }
    abstract class AbstractBar {}
    class ConcreteBar : AbstractBar {}

    abstract class AbstractFoo
    {
        public abstract AbstractBar getBar();
    }
    class ConcreteFoo : AbstractFoo
    {
        public override AbstractBar getBar()
        {
            return new ConcreteBar();
        }
    }
}