public interface IDocumentComponent
    {
        string GatherData();
        void AddComponent(IDocumentComponent documentComponent);
    }

    public class CustomerDocumentComponent : IDocumentComponent
    {
        private int CustomerIdToGatherData { get; set; }

        public CustomerDocumentComponent(int customerIdToGatherData)
        {
            CustomerIdToGatherData = customerIdToGatherData;
        }

        public string GatherData()
        {
            string customerData;
            switch (CustomerIdToGatherData)
            {
                case 41:
                    customerData = "Andriy Buday";
                    break;
                default:
                    customerData = "Someone else";
                    break;
            }

            return string.Format("<Customer>{0}</Customer>", customerData);
        }

        public void AddComponent(IDocumentComponent documentComponent)
        {
            Console.WriteLine("Cannot add to leaf...");
        }
    }

    public class DocumentComponent : IDocumentComponent
    {
        public string Name { get; private set; }
        public List<IDocumentComponent> DocumentComponents { get; private set; }

        public DocumentComponent(string name)
        {
            Name = name;
            DocumentComponents = new List<IDocumentComponent>();
        }

        public string GatherData()
        {
            var stringBuilder = new StringBuilder();
            stringBuilder.AppendLine(string.Format("<{0}>", Name));
            foreach (var documentComponent in DocumentComponents)
            {
                documentComponent.GatherData();
                stringBuilder.AppendLine(documentComponent.GatherData());
            }
            stringBuilder.AppendLine(string.Format("</{0}>", Name));

            return stringBuilder.ToString();
        }

        public void AddComponent(IDocumentComponent documentComponent)
        {
            DocumentComponents.Add(documentComponent);
        }
    }

            var document = new DocumentComponent("ComposableDocument");
            var headerDocumentSection = new HeaderDocumentComponent();
            var body = new DocumentComponent("Body");
            document.AddComponent(headerDocumentSection);
            document.AddComponent(body);

            var customerDocumentSection = new CustomerDocumentComponent(41);
            var orders = new DocumentComponent("Orders");
            var order0 = new OrderDocumentComponent(0);
            var order1 = new OrderDocumentComponent(1);
            orders.AddComponent(order0);
            orders.AddComponent(order1);

            body.AddComponent(customerDocumentSection);
            body.AddComponent(orders);

            string gatheredData = document.GatherData();

            Console.WriteLine(gatheredData);

            var customer = new Customer();

            // for some reason boss always knows that company has money
            // only for team Z
            var team = new Team("Z");
            // he also managed to get high-level list of requirements for you
            var requirements = new List<Requirement>() { new Requirement("Cool web site"), new Requirement("Ability to book beer on site") };
            // you should be ready to be invoked by Customer
            ICommand commandX = new YouAsProjectManagerCommand(team, requirements);

            customer.AddCommand(commandX);

            // there is also here developer who can code at light speed
            var heroDeveloper = new HeroDeveloper();
            // boss decided to give him project A
            ICommand commandA = new HeroDeveloperCommand(heroDeveloper, "A");

            customer.AddCommand(commandA);

            // when customer signs contract with boss
            // your team and hero developer start executing their job
            customer.SignContractWithBoss();

    public interface ICommand
    {
        void Execute();
    }


    public class YouAsProjectManagerCommand : ICommand
    {
        public YouAsProjectManagerCommand(Team team, List<Requirement> requirements)
        {
            Team = team;
            Requirements = requirements;
        }

        public void Execute()
        {
            // implementation delegates work to concrete receiver
            Team.CompleteProject(Requirements);
        }

        protected Team Team { get; set; }
        protected List<Requirement> Requirements { get; set; }
    }

    public class HeroDeveloperCommand : ICommand
    {
        public HeroDeveloperCommand(HeroDeveloper heroDeveloper, string projectName)
        {
            HeroDeveloper = heroDeveloper;
            ProjectName = projectName;
        }

        protected HeroDeveloper HeroDeveloper { get; set; }
        public string ProjectName { get; set; }

        public void Execute()
        {
            // implementation delegates work to concrete receiver
            HeroDeveloper.DoAllHardWork(ProjectName);
        }
    }

    public class Customer
    {
        public Customer()
        {
            Commands = new List<ICommand>();
        }

        public void AddCommand(ICommand command)
        {
            Commands.Add(command);
        }

        protected List<ICommand> Commands { get; set; }

        public void SignContractWithBoss()
        {
            foreach (var command in Commands)
            {
                command.Execute();
            }
        }
    }

    internal interface IBuldingCompany
    {
        void BuildFoundation();
        void BuildRoom();
        void BuildRoof();

        IWallCreator WallCreator { get; set; }
    }

    internal class BuldingCompany : IBuldingCompany
    {
        public void BuildFoundation()
        {
            Console.WriteLine("Foundation is built.{0}", Environment.NewLine);
        }

        public void BuildRoom()
        {
            WallCreator.BuildWallWithDoor();
            WallCreator.BuildWall();
            WallCreator.BuildWallWithWindow();
            WallCreator.BuildWall();

            Console.WriteLine("Room finished.{0}", Environment.NewLine);
        }

        public IWallCreator WallCreator { get; set; }

        public void BuildRoof()
        {
            Console.WriteLine("Roof is done.{0}", Environment.NewLine);
        }
    }

            // We have two wall creating crews - concrete blocks one and bricks one
            var brickWallCreator = new BrickWallCreator();
            var conctreteSlabWallCreator = new ConcreteSlabWallCreator();

            var buildingCompany = new BuldingCompany();
            buildingCompany.BuildFoundation();

            buildingCompany.WallCreator = conctreteSlabWallCreator;
            buildingCompany.BuildRoom();

            // Company can easily switch to another wall crew to continue building rooms
            // with another material
            buildingCompany.WallCreator = brickWallCreator;
            buildingCompany.BuildRoom();
            buildingCompany.BuildRoom();

            buildingCompany.BuildRoof();