C# 标准事件流实例代码

public class eventstandard
  {
    public class clothes {

      /// <summary>
      /// 服装编码
      /// </summary>
      public string id { get; set; }

      /// <summary>
      /// 服装名称
      /// </summary>
      public string name { get; set; }

      /// <summary>
      /// 服装价格
      /// </summary>
      private double _price;

      public double price {
        get { return this._price; }
        set {
            pricerisehandler?.invoke(this, new priceeventargs()
            {
              oldprice = this._price,
              newprice = value
            });
          this._price = value;
        }
      }

      /// <summary>
      /// 服装价格变动事件
      /// </summary>
      public event eventhandler pricerisehandler;

    }

    /// <summary>
    /// 衣服价格事件参数 一般会为特定的事件去封装个参数类型
    /// </summary>
    public class priceeventargs : eventargs
    {
      public double oldprice { get; set; }
      public double newprice { get; set; }
    }

    public class taobao {
      /// <summary>
      /// 淘宝订户
      /// </summary>
      public void publishpriceinfo(object sender, eventargs e) {
        clothes clothes = (clothes)sender;
        priceeventargs args = (priceeventargs)e;
        if (args.newprice < args.oldprice)
          console.writeline($"淘宝：发布衣服价格下降的公告，{clothes.name}服装直降{args.oldprice - args.newprice}元，限时抢购！");
        else
          console.writeline("淘宝：价格悄悄上涨或价格未变化，啥也不做");
      }

    }

    public class consumer
    {
      /// <summary>
      /// 消费者订户
      /// </summary>
      public void buy(object sender, eventargs e)
      {
        clothes clothes = (clothes)sender;
        priceeventargs args = (priceeventargs)e;
        if (args.newprice < args.oldprice)
          console.writeline($"消费者：之前价格{args.oldprice}，现在价格{args.newprice},果断买了！");
        else
          console.writeline($"消费者：等等看，降价了再说");
      }
    }

    public static void show()
    {
      clothes clothes = new clothes()
      {
        id = "12111-xk",
        name = "优衣库",
        price = 128
      };
      //订阅：把订户和发布者的事件关联起来
      clothes.pricerisehandler += new taobao().publishpriceinfo;
      clothes.pricerisehandler += new consumer().buy;
      //价格变化，自动触发订户订阅的事件
      clothes.price = 300;
    }

  }

clothes.price = 300; 
eventstandard.show();

clothes.price = 98; 
eventstandard.show();