C#代码精粹

ArreyList

1. 请简述ArreyList和数组的区别
   ArreyList本质上是一个object数组的封装
   区别：
   (1)而数组在使用时候需要定长，ArreyList可以一开始就不用定长。
   (2)数组可以指定存储类型，ArreyList默认为object类型。
   (3)数组的增删需要我们自己去实现，Arraylist帮我们封装好了方便使用的API。
   (4)数组只要不是object就不存在装箱拆箱，而ArrayList存在。
   (5)数组长度为Length，ArrayList长度为Count。
2. 创建一个背包类，使用ArrayList存储物品，实现购买物品，卖出物品，显示物品功能，买入或卖出物品会导致金钱变化

   using System.Collections;
   using System.Reflection.Metadata.Ecma335;
   
   namespace C__01
   {
       public class Item
       {
           public int id;
           public string name;
           public int price;
           public int number;
           public Item(int id, string name, int price, int number)
           {
               this.id = id;
               this.name = name;
               this.price = price;
               this.number = number;
           }
       }
       public class backPack
       {
           public ArrayList items;
           private int money;
           public backPack(int money)
           {
               this.items = new ArrayList();
               this.money = money;
           }
   
               public void buyItems(Item item)
           {
               if (item.id <= 0 || item.price <= 0)
               {
                   Console.WriteLine("Item Doesn't Exist！");
                   return;
               }
               //如果钱不够直接跳出
               if (this.money < item.price * item.number)
               {
                   Console.WriteLine("Need More Cash!");
                   return;
               }
               //花钱并打印信息
               money = money - (item.price * item.number);
               Console.WriteLine("购买{0}{1}个花费{2}钱", item.name, item.number, item.price * item.number);
               if (items.Count == 0)
               {
                   items.Add(item);
               }
               else
               {
                   //遍历添加物品
                   for (int i = 0; i <= items.Count; i++)
                   {
                       //如果已经存在，叠加物品
                       if ((items[i] as Item).id == item.id)
                       {
                           (items[i] as Item).number += item.number;
                           return;
                       }
                       //否则添加新物品
                       if ((items[i] as Item).id != item.id)
                       {
                           items.Add(item);
                           return;
                       }
   
                   }
   
               }
           }
               public void sellItems(Item item)
               {
                   int num = 0;
                   for (int j = 0; j < items.Count; j++)
                   {
                       if ((items[j] as Item).id == item.id)
                       {
                           if ((items[j] as Item).number > item.number)
                           {
                               num = item.number;
                           }
                           else
                           {
                               num = (items[j] as Item).number;
                               items.RemoveAt(j);
                           }
   
                           int sellMoney = (int)(item.price * item.number * 0.8f);
                           money = money + sellMoney;
   
                           Console.WriteLine("卖了{0}{1}个，赚了{2}元", item.name, item.number, sellMoney);
                           Console.WriteLine("还剩{0}元", this.money);
                       }
                   }
               }
               public void showItems()
               {
                   Item item;
                   for (int index = 0; index < items.Count; index++)
                   {
                       item = items[index] as Item;
                       Console.WriteLine("有{0}{1}个", item.name, item.number);
                   }
                   Console.WriteLine("有{0}钱", this.money);
               }
   
           }
           internal class Program
           {
               static void Main(string[] args)
               {
                   backPack bag = new backPack(10000);
                   Item Throwingknife = new Item(1, "Throwingknife", 50, 5);
                   Item bullets = new Item(2, "Bullets", 100, 3);
                   Item Armor = new Item(3, "Armor", 1000, 1);
                   Item TTI2011 = new Item(4, "Pistol", 7000, 1);
   
   
                   bag.buyItems(Armor);
                   bag.buyItems(Throwingknife);
                   bag.buyItems(TTI2011);
                   bag.buyItems(bullets);
                   Console.WriteLine(bag.items.Count);
                   bag.sellItems(Throwingknife);
                   bag.showItems();
               }
           }
   }