class Item
 {
  private int _key;
  public int Key
  {
   get
   {
    return _key;
   }
   set
   {
    _key = value;
   }
  }

  private string _ItemName;

  public string ItemName
  {
   get { return _ItemName; }
   set { _ItemName = value; }
  }

  public Item()
  {

  }

  public Item(int key, string itemName)
  {
   this._key = key;
   this._ItemName = itemName;
  }

  public override string ToString()
  {
   return string.Format("ID: {0}; Name: {1}。",_key,_ItemName);
  }
 }

class ShoppingCart
 {
  private SortedList<int, Item> _sl = new SortedList<int, Item>();

  public void Add(Item item) //物件添加
  {
   this._sl.Add(item.Key, item);
  }

  public void Edit(Item item) //编辑物件
  {
   if (this._sl.ContainsKey(item.Key))
   {
    this._sl[item.Key] = item;
   }
  }

  public void Delete(Item item) //删除物件
  {
   this._sl.Remove(item.Key);
  }

  public Item this[int key] //索引器
  {
   get
   {
    if (!this._sl.ContainsKey(key))
    {
     return null;
    }
    else
    {
     return this._sl[key];
    }
   }
  }

  public virtual int Count //集合中物件数量
  {
   get
   {
    return this._sl.Count;
   }
  }

  public virtual IEnumerable<Item> Items //获取所有物件
  {
   get
   {
    return this._sl.Values;
   }
  }
 }

class Program
 {
  static void Main(string[] args)
  {
   ShoppingCart sc = new ShoppingCart();

   var item1 = new Collections.Item();
   item1.Key = 1;
   item1.ItemName = "Huawei V8";
   sc.Add(item1);

   var item2 = new Collections.Item();
   item2.Key = 2;
   item2.ItemName = "Huawei V9";
   sc.Add(item2);

   var item3 = new Collections.Item();
   item3.Key = 3;
   item3.ItemName = "Huawei V10";
   sc.Add(item3);

   Console.WriteLine("使用索引器，输出对象：");
   Console.WriteLine(sc[3].ToString());

   Console.WriteLine("集合中对象数量：");
   Console.WriteLine(sc.Count);

   Console.WriteLine("列出所有对象：");
   sc.Items.ForEach(delegate (Collections.Item item)
   {
    Console.WriteLine(item.ToString());
   });
  }
 }

var item4 = new Collections.Item();
   item4.Key = 2;
   item4.ItemName = "Huawei Mate10";
   sc.Edit(item4);

   Console.WriteLine("编辑后列出所有对象：");
   sc.Items.ForEach(delegate (Collections.Item item)
   {
    Console.WriteLine(item.ToString());
   });


   var item5 = new Collections.Item();
   item5.Key = 1;
   sc.Delete(item5);

   Console.WriteLine("删除后列出所有对象：");
   sc.Items.ForEach(delegate (Collections.Item item)
   {
    Console.WriteLine(item.ToString());
   });