用最简单的例子理解复合模式(Composite Pattern)

在显示树形结构时，复合模式有很好的体现。本篇显示如下部门结构：

以上，有的节点包含子节点，有的节点部包含子节点。不管是什么节点，每个节点就代表一个部门。

首先设计一个关于部门的抽象基类。

    public abstract class DepartmentComponent

    {

        public string Name { private set; get; }


        public DepartmentComponent(string name)

        {

            this.Name = name;

        }


        public virtual void PrintSupervisorOf(int spacing)

        {

            for (int counter = 0; counter < spacing; counter++)

            {

                Console.Write(" ");

            }

            Console.WriteLine(Name);

        }

    }

以上，通过构造函数给属性赋值，通过PrintSupervisorOf(int spacing)方法打印出节点的名称。

接下来设计包含子节点的节点。该类维护着DepartmentComponent类型的集合，提供方法向这个集合中添加节点或从集合中删除节点。

    public class DepartmentComposite : DepartmentComponent

    {

        private IList<DepartmentComponent> employees;


        public DepartmentComposite(string name) : base(name)

        {

            employees = new List<DepartmentComponent>();

        }


        public void AddDepartment(DepartmentComponent e)

        {

            employees.Add(e);

        }


        public void RemoveDepartment(DepartmentComponent e)

        {

            employees.Remove(e);

        }


        public override void PrintSupervisorOf(int spacing)

        {

            base.PrintSupervisorOf(spacing);


            foreach (DepartmentComponent e in employees)

            {

                e.PrintSupervisorOf(spacing + 1);

            }

        }

    }

以上 PrintSupervisorOf(int spacing)方法重写了抽象基类的方法，不仅把本节点的名称打印出来，还使用递归把所有子节点的名称显示出来。

最后设计部包含子节点的节点。

    public class Department : DepartmentComponent

    {

        public Department(string name) : base(name)

        {


        }


        public override void PrintSupervisorOf(int spacing)

        {

            base.PrintSupervisorOf(spacing);

        }

    }

客户端部分。

    class Program

    {

        static void Main(string[] args)

        {

            DepartmentComposite salesDepartment1 = new DepartmentComposite("销售部1");

            Department zhangsan = new Department("张三");

            Department lisi = new Department("李四");


            DepartmentComposite salesDepartment2 = new DepartmentComposite("销售部2");

            DepartmentComposite specialDepartment = new DepartmentComposite("销售部2特别行动组");

            Department wangwu = new Department("王五");

            Department zhaoliu = new Department("赵六");


            DepartmentComposite salesDepartment = new DepartmentComposite("销售部");

            salesDepartment.AddDepartment(salesDepartment1);

            salesDepartment.AddDepartment(salesDepartment2);


            salesDepartment1.AddDepartment(zhangsan);

            salesDepartment1.AddDepartment(lisi);


            salesDepartment2.AddDepartment(specialDepartment);


            specialDepartment.AddDepartment(wangwu);

            specialDepartment.AddDepartment(zhaoliu);


            salesDepartment.PrintSupervisorOf(0);

            Console.ReadKey();

        }

    }