C#標準事件流

服裝價格變更，觸發淘寶發佈活動和消費者購買衣服事件流

 1     public class EventStandard
 2     {
 3         public class Clothes {
 4 
 5             /// <summary>
 6             /// 服裝編碼
 7             /// </summary>
 8             public string Id { get; set; }
 9 
10             /// <summary>
11             /// 服裝名稱
12             /// </summary>
13             public string Name { get; set; }
14 
15             /// <summary>
16             /// 服裝價格
17             /// </summary>
18             private double _price;
19 
20             public double Price {
21                 get { return this._price; }
22                 set {
23                         PriceRiseHandler?.Invoke(this, new PriceEventArgs()
24                         {
25                             OldPrice = this._price,
26                             NewPrice = value
27                         });
28                     this._price = value;
29                 }
30             }
31 
32             /// <summary>
33             /// 服裝價格變更事件
34             /// </summary>
35             public event EventHandler PriceRiseHandler;
36 
37         }
38 
39         /// <summary>
40         /// 衣服價格事件參數  通常會爲特定的事件去封裝個參數類型
41         /// </summary>
42         public class PriceEventArgs : EventArgs
43         {
44             public double OldPrice { get; set; }
45             public double NewPrice { get; set; }
46         }
47 
48         public class TaoBao {
49             /// <summary>
50             /// 淘寶訂戶
51             /// </summary>
52             public void PublishPriceInfo(object sender, EventArgs e) {
53                 Clothes clothes = (Clothes)sender;
54                 PriceEventArgs args = (PriceEventArgs)e;
55                 if (args.NewPrice < args.OldPrice)
56                     Console.WriteLine($"淘寶：發佈衣服價格降低的公告，{clothes.Name}服裝直降{args.OldPrice - args.NewPrice}元，限時搶購！");
57                 else 
58                     Console.WriteLine("淘寶：價格悄悄上漲或價格未變化，啥也不作");
59             }
60 
61         }
62 
63         public class Consumer
64         {
65             /// <summary>
66             /// 消費者訂戶
67             /// </summary>
68             public void Buy(object sender, EventArgs e)
69             {
70                 Clothes clothes = (Clothes)sender;
71                 PriceEventArgs args = (PriceEventArgs)e;
72                 if (args.NewPrice < args.OldPrice)
73                     Console.WriteLine($"消費者：以前價格{args.OldPrice}，如今價格{args.NewPrice},果斷買了！");
74                 else 
75                     Console.WriteLine($"消費者：等等看，降價了再說");
76             }
77         }
78 
79         public static void Show()
80         {
81             Clothes  clothes = new Clothes()
82             {
83                 Id = "12111-XK",
84                 Name = "優衣庫",
85                 Price = 128
86             };
87             //訂閱：把訂戶和發佈者的事件關聯起來
88             clothes.PriceRiseHandler += new TaoBao().PublishPriceInfo;
89             clothes.PriceRiseHandler += new Consumer().Buy;
90             //價格變化，自動觸發訂戶訂閱的事件
91             clothes.Price = 300;
92         }
93 
94     }

 調用：

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

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