组合（Composite）模式 *

     // 创建一个树结构
            Composite root = new Composite("root");
            root.Add(new Leaf("Leaf A"));
            root.Add(new Leaf("Leaf B"));
            Composite comp = new Composite("Composite X");

            comp.Add(new Leaf("Leaf XA"));
            comp.Add(new Leaf("Leaf XB"));
            root.Add(comp);
            Composite compss = new Composite("Composite Y");
            compss.Add(new Leaf("Leaf XXB"));
            comp.Add(compss);
            root.Add(new Leaf("Leaf C"));
            // 添加和删除叶子
            Leaf l = new Leaf("Leaf D");
            root.Add(l);
            root.Remove(l);

            // 递归地显示节点
            root.Display(1);

            Console.WriteLine("\n ============ \n");


    /// <summary>
    /// 抽象构件(Component)角色
    /// </summary>
    public abstract class Component
    {
        protected string name; 
        // 构造函数
        public Component(string name)
        {
            this.name = name;
        }
        // 操作
        public abstract void Display(int depth);
    }

    //  树枝构件（Composite）角色
    public class Composite : Component
    { 
        private ArrayList children = new ArrayList(); 
        //构造函数
        public Composite(string name) : base(name) { } 

        //方法
        public void Add(Component component)
        {
            children.Add(component);
        }
        public void Remove(Component component)
        {
            children.Remove(component);
        } 
        
        public override void Display(int depth)
        {
            Console.WriteLine(new String(‘-‘, depth) + name); 
            // 显示每个节点的孩子
            foreach (Component component in children)
                component.Display(depth + 3);
        }  
    }
    /// <summary>
    /// 树叶构件（Leaf）角色
    /// </summary>
    public class Leaf : Component
    {
        // 构造函数
        public Leaf(string name) : base(name) { } 
        // 从写函数
        public override void Display(int depth)
        {
            Console.WriteLine(new String(‘-‘, depth) + name);
        }
    }