composite-theory-ns.cs

  using System;
  using System.Collections.Generic;
  using System.Text; // for StringBuilder

  namespace CompositePattern {
    // The Interface
    public interface IComponent <T> {
      void Add(IComponent <T> c);
      IComponent <T> Remove(T s);
      string Display(int depth);
      IComponent <T> Find(T s);
      T Name {get; set;}
    }

    // The Composite
    public class Composite <T> : IComponent  <T> {
      List  <IComponent <T>> list = null;

      public T Name {get; set;}
    
      public Composite (T name)  {
        Name = name;
        list = new List <IComponent <T>> ();
      }

      public void Add(IComponent  <T> c) {
        list.Add(c);
      }

      // Finds the item from a particular point in the structure
      // and returns the composite from which it was removed
      // If not found, return the point as given
      public IComponent <T> Remove(T s) {
        holder = this;
        IComponent <T> p = holder.Find(s);
        if (holder!=null) {
           (holder as Composite<T>).list.Remove(p);
           return holder;
        }
        else
           return this;
      }
    
      IComponent <T> holder=null;
    
      // Recursively looks for an item
      // Returns its reference or else null
      public IComponent <T>  Find (T s) {
        holder = this;
        if (Name.Equals(s)) return this;
        IComponent <T> found=null;
        foreach (IComponent <T> c in list)  {
          found = c.Find(s);
          if (found!=null)
            break;
        }
        return found;
      }
    
      // Displays items in a format indicating their level in the composite structure
      public string Display(int depth) {
        StringBuilder s = new StringBuilder(new String('-', depth));
        s.Append("Set "+ Name +  " length :" + list.Count + "\n");
        foreach (IComponent <T> component in list) {
          s.Append(component.Display(depth + 2));
        }
        return s.ToString();
      }
    }

    // The Component
    public class Component <T> : IComponent <T> {
      public T Name {get; set;}
    
      public Component (T name)  {
        Name = name;
      }

      public void Add(IComponent <T> c) {
        Console.WriteLine("Cannot add to an item");
      }

      public IComponent <T>  Remove(T s) {
        Console.WriteLine("Cannot remove directly");
        return this;
      }

      public string Display(int depth) {
      return new String('-', depth) + Name+"\n";
      }
    
      public IComponent <T>  Find (T s) {
        if (s.Equals(Name))
          return this;
        else
            return null;
      }
    }
  }