[.net core]9.中间件的具体实现

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.Run(async (context) =>
            {
                await context.Response.WriteAsync(_config["MyKey"]);
            });
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.Use(async (context, next) =>
            {
                Console.WriteLine("步骤1:中间件1处理");
                await next();
                Console.WriteLine("步骤7:中间件1响应回调");
                
            });

            app.Use(async (context, next) =>
            {
                Console.WriteLine("步骤2:中间件2处理");
                await next();
                Console.WriteLine("步骤6:中间件2响应回调");
                
            });
            app.Use(async (context, next) =>
            {
                Console.WriteLine("步骤3:中间件3处理");
                await next();
                Console.WriteLine("步骤5:中间件3响应回调");
                
            });

            app.Run(async (context) =>
            {
                //在这里产生响应
                await context.Response.WriteAsync("产生响应");
                Console.WriteLine("步骤4:响应回调");
            });
        }

                context.Response.Headers["Content-Type"] = "application/json";