C#标准事件流

服装价格变动，触发淘宝发布活动和消费者购买衣服事件流

    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;
        }

    }

调用

clothes.Price = 300; 
EventStandard.Show();

clothes.Price = 98; 
EventStandard.Show();