Aaron.cs

namespace Patterns.AbstractFactory.People
{
    using Patterns.AbstractFactory.Drinks;

    /// <summary>
    /// The aaron.
    /// </summary>
    public class Aaron : ICocktailFactory
    {
        /// <summary>
        /// The favorite drink.
        /// </summary>
        /// <returns>
        /// The <see cref="IDrink"/>.
        /// </returns>
        public IDrink FavoriteDrink()
        {
            return new StirredMartini();
        }
    }
}

BarPerson.cs

namespace Patterns.AbstractFactory
{
    using Patterns.AbstractFactory.Drinks;
    using Patterns.AbstractFactory.People;

    /// <summary>
    /// The bar person.
    /// </summary>
    public class BarPerson : IBarPerson 
    {
        /// <summary>
        /// The mix drink.
        /// </summary>
        /// <typeparam name="T">
        /// The factory that supplies the drink to me made.
        /// </typeparam>
        /// <returns>
        /// The <see cref="IDrink"/>.
        /// </returns>
        public IDrink MixDrink<T>() where T : ICocktailFactory, new()
        {
            return new T().FavoriteDrink();
        }
    }
}

BarPersonTests.cs

namespace Patterns.AbstractFactory
{
    using NUnit.Framework;

    using Patterns.AbstractFactory.Drinks;
    using Patterns.AbstractFactory.People;

    [TestFixture]
    public class BarPersonTests
    {
        [Test]
        public void CanCreateShakenMartiniForMrBond()
        {
            var barPerson = new BarPerson();
            var drink = barPerson.MixDrink<MrBond>();

            Assert.That(drink, Is.TypeOf<ShakenMartini>());
        }

        [Test]
        public void CanCreateStirredMartiniForAaron()
        {
            var barPerson = new BarPerson();
            var drink = barPerson.MixDrink<Aaron>();

            Assert.That(drink, Is.TypeOf<StirredMartini>());
        }

        [Test]
        public void CanCreateCoffeeMartiniForScott()
        {
            var barPerson = new BarPerson();
            var drink = barPerson.MixDrink<Scott>();

            Assert.That(drink, Is.TypeOf<CoffeeMartini>());
        }
    }
}

MrBond.cs

namespace Patterns.AbstractFactory.People
{
    using Patterns.AbstractFactory.Drinks;

    /// <summary>
    /// The mr bond.
    /// </summary>
    public class MrBond : ICocktailFactory
    {
        /// <summary>
        /// The favorite drink.
        /// </summary>
        /// <returns>
        /// The <see cref="IDrink"/>.
        /// </returns>
        public IDrink FavoriteDrink()
        {
            return new ShakenMartini();
        }
    }
}

Scott.cs

namespace Patterns.AbstractFactory.People
{
    using Patterns.AbstractFactory.Drinks;

    /// <summary>
    /// The scott.
    /// </summary>
    public class Scott : ICocktailFactory
    {
        /// <summary>
        /// The favorite drink.
        /// </summary>
        /// <returns>
        /// The <see cref="IDrink"/>.
        /// </returns>
        public IDrink FavoriteDrink()
        {
            return new CoffeeMartini();
        }
    }
}