/// <summary>
  /// 一個抽象構件，聲明一個接口用于訪問和管理Component的子部件
  /// </summary>
  public abstract class Component
  {
    protected string name;

    public Component(string name)
    {
      this.name = name;
    }

    /// <summary>
    /// 增加一個節(jié)點
    /// </summary>
    /// <param name="component"></param>
    public abstract void Add(Component component);

    /// <summary>
    /// 移除一個節(jié)點
    /// </summary>
    /// <param name="component"></param>
    public abstract void Remove(Component component);

    /// <summary>
    /// 顯示層級結構
    /// </summary>
    public abstract void Display(int level);
  }

  /// <summary>
  /// 葉子節(jié)點
  /// </summary>
  public class Leaf : Component
  {
    public Leaf(string name)
      : base(name)
    { }

    /// <summary>
    /// 由于葉子節(jié)點沒有子節(jié)點，所以Add和Remove方法對它來說沒有意義，但它繼承自Component，這樣做可以消除葉節(jié)點和枝節(jié)點對象在抽象層次的區(qū)別，它們具備完全一致的接口。
    /// </summary>
    /// <param name="component"></param>
    public override void Add(Component component)
    {
      Console.WriteLine("Can not add a component to a leaf.");
    }

    /// <summary>
    /// 實現它沒有意義，只是提供了一個一致的調用接口
    /// </summary>
    /// <param name="component"></param>
    public override void Remove(Component component)
    {
      Console.WriteLine("Can not remove a component to a leaf.");
    }

    public override void Display(int level)
    {
      Console.WriteLine(new string('-',level) + name);
    }
  }

  /// <summary>
  /// 定義有枝節(jié)點的行為，用來存儲部件，實現在Component接口中對子部件有關的操作
  /// </summary>
  public class Composite : Component
  {
    public Composite(string name)
      : base(name)
    { }

    /// <summary>
    /// 一個子對象集合，用來存儲其下屬的枝節(jié)點和葉節(jié)點
    /// </summary>
    private List<Component> children = new List<Component>();

    /// <summary>
    /// 增加子節(jié)點
    /// </summary>
    /// <param name="component"></param>
    public override void Add(Component component)
    {
      children.Add(component);
    }

    /// <summary>
    /// 移除子節(jié)點
    /// </summary>
    /// <param name="component"></param>
    public override void Remove(Component component)
    {
      children.Remove(component);
    }

    public override void Display(int level)
    {
      Console.WriteLine(new string('-', level) + name);

      // 遍歷其子節(jié)點并顯示
      foreach (Component component in children)
      {
        component.Display(level+2);
      }
    }
  }

  class Program
  {
    static void Main(string[] args)
    {
      // 生成樹根，并為其增加兩個葉子節(jié)點
      Component root = new Composite("Root");
      root.Add(new Leaf("Leaf A in Root"));
      root.Add(new Leaf("Leaf B in Root"));

      // 為根增加兩個枝節(jié)點
      Component branchX = new Composite("Branch X in Root");
      Component branchY = new Composite("Branch Y in Root");
      root.Add(branchX);
      root.Add(branchY);

      // 為BranchX增加頁節(jié)點
      branchX.Add(new Leaf("Leaf A in Branch X"));

      // 為BranchX增加枝節(jié)點
      Component branchZ = new Composite("Branch Z in Branch X");
      branchX.Add(branchZ);

      // 為BranchY增加葉節(jié)點
      branchY.Add(new Leaf("Leaf in Branch Y"));

      // 為BranchZ增加葉節(jié)點
      branchZ.Add(new Leaf("Leaf in Branch Z"));

      // 顯示樹
      root.Display(1);

      Console.Read();
    }
  }