中间件执行顺序（管道）

 1 using System.Threading.Tasks;
 2 using Microsoft.AspNetCore.Hosting;
 3 using Microsoft.AspNetCore.Http;
 4 using Microsoft.Extensions.Hosting;
 5 
 6 namespace ConsoleApp2
 7 {
 8     public static class Sample02
 9     {
10 
11         public static void Start()
12         {
13 
14             var host = Host.CreateDefaultBuilder()
15                 .ConfigureWebHostDefaults(builder => builder
16                     .Configure(app => app
17                         .Use(Middleware1)                           //使用中间件
18                         .Use(Middleware2)
19                     )
20                 ).Build();
21             host.Run();
22         }
23 
24         private static RequestDelegate Middleware1(RequestDelegate next)
25         {
26             async Task App(HttpContext context)
27             {
28                 await context.Response.WriteAsync("Middleware 1 Begin.");     //Step 1
29                 await next(context);                                         //跳转到下一个中间件
30                 await context.Response.WriteAsync("Middleware 1 End.");       //Step3
31             }
32 
33             return App;
34         }
35 
36 
37         private static RequestDelegate Middleware2(RequestDelegate next)
38         {
39             async Task App(HttpContext context)
40             {
41                 await context.Response.WriteAsync("Middleware 2 Begin.");        //没有就返回 //Step2
42             }
43 
44             return App;
45         }
46     }
47 }