C#异步和等待流

码：

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.Owin;
using Microsoft.Owin.Hosting;
using Owin;
namespace KatanaConsole
{
    //use an alias for OWIN APPFunc
    using AppFunc= Func<IDictionary<string,object>,Task>;
    class Program
    {
        static void Main(string[] args)
        {

            var uri = "http://localhost:8080";

            using ( WebApp.Start<StartUp>(uri))
            {
                Console.WriteLine("Web Server started on port 2323");
                 Console.WriteLine("Server Started; Press enter to Quit");
                Console.ReadLine();
            }
        }
    }

    public class StartUp
    {
        public void Configuration(IAppBuilder appBuilder)
        {
        var firstMiddleware= new Func<AppFunc,AppFunc>(FirstMiddleware);
        var secondMiddleware = new Func<AppFunc,AppFunc>(SecondMiddleware);

        appBuilder.Use(firstMiddleware);
        appBuilder.Use(secondMiddleware);

        }


        public AppFunc FirstMiddleware(AppFunc next)
        {

            AppFunc appFunc = async environment =>
            {
                IOwinContext context = new OwinContext(environment);
                await context.Response.WriteAsync("<h1> Middleware:1 ->  Hello from X1</h1>");
                await next.Invoke(environment);
            };
            return appFunc;
        }

        public AppFunc SecondMiddleware(AppFunc next)
        {

            AppFunc appFunc = async (IDictionary<string,object> environment) =>
            {
                IOwinContext context = new OwinContext(environment);
                await context.Response.WriteAsync("<h1> Middleware:2 ->  Hello from X2</h1>");
                await next.Invoke(environment);
            };
            return appFunc;
        }
    }


}

我尝试访问localhost时的代码流：8080

流：

进入 – >第一个中间件

> IOwinContext context = new OwinContext(environment);
> await context.Response.WriteAsync(“< h1> Middleware：1 – > Hello from from
X1< / h1>“); //响应发送到浏览器
>等待next.Invoke(环境);

进入 – >第二个中间件

> IOwinContext context = new OwinContext(environment);
> await context.Response.WriteAsync(“< h1> Middleware：2 – > Hello from from
X2< / h1>“); //响应发送到浏览器
>等待next.Invoke(环境);

进入(返回呼叫方法) – >第一个中间件

>等待next.Invoke(环境);
>退出 – > FirstMiddleWare

重新进入 – >第一个中间件

> IOwinContext context = new OwinContext(environment);
> await context.Response.WriteAsync(“< h1> Middleware：1 – > Hello from from
?X1< / h1>“); //无响应发送到浏览器
>等待next.Invoke(环境);

重新进入 – >第二个中间件

> IOwinContext context = new OwinContext(environment);
> await context.Response.WriteAsync(“< h1> Middleware：2 – > Hello from from
??????X2< / h1>“); //无响应发送到浏览器
>等待next.Invoke(环境);

重新进入(返回呼叫方法) – >第一个中间件

>等待next.Invoke(环境);
>退出 – > FirstMiddleWare

执行停止
我的问题是为什么它再次遍历第9步和第16步？

并添加到它,即使遍历步骤9和16,响应也不会改变.所以我猜它在那里进行一些后置条件检查.

**编辑 – 1 **

添加了所有遍历的步骤以使其更加清晰(添加了步骤9到16)