using System;

using System.Collections.Generic;

using System.Diagnostics;

​

// Abstract Factory with generics to be used everywhere we need it

​

namespace AbstractFactory

{

    public interface ICreator<BaseType>

    {

        BaseType Create();

    }

​

    public class DerivedCreator<Derived, Base> : ICreator<Base>

        where Derived : Base, new()

    {

        public Base Create()

        {

            return new Derived();

        }

    }

​

    public class Factory<Key, Base>

    {

        private Dictionary<Key, ICreator<Base>> _map;

​

        public Factory()

        {

            _map = new Dictionary<Key, ICreator<Base>>();

        }

​

        public void Register(Key key, ICreator<Base> creator)

        {

            Debug.Assert(!_map.ContainsKey(key), "key is already registered.");

            _map.Add(key, creator);

        }

​

        public Base Create(Key key)

        {

            Debug.Assert(_map.ContainsKey(key), "key is not registered");

            return _map[key].Create();

        }

    }

}

​

// ActivityFactory : example to use the abstract factory

​

public class AbstractActivity

{

}

​

public class ActivityOne : AbstractActivity

{

    public ActivityOne()

    {

        Console.WriteLine("ActivityOne created");

    }

}

​

public class ActivityTwo : AbstractActivity

{

    public ActivityTwo()

    {

        Console.WriteLine("ActivityTwo created");

    }

}

​

public class DerivedActivityCreator<Derived> : AbstractFactory.DerivedCreator<Derived, AbstractActivity>

    where Derived : AbstractActivity, new()

{

}

​

public class ActivityFactory

{

    private AbstractFactory.Factory<String, AbstractActivity> _factory;

​

    public ActivityFactory()

    {

        _factory = new AbstractFactory.Factory<String, AbstractActivity>();

        _factory.Register("ActivityOne", new DerivedActivityCreator<ActivityOne>());

        _factory.Register("ActivityTwo", new DerivedActivityCreator<ActivityTwo>());

    }

​

    public AbstractActivity Create(String key)

    {

        return _factory.Create(key);

    }

}

​

​

public class Program

{

    public static void Main(string[] args)

    {

        var activityFactory = new ActivityFactory();

        var activity = activityFactory.Create("ActivityOne");

    }

}

​

​