dotNetCore阅读源码-UseRouting及UseEndpoints内部

UseRouting内部：

  public static IApplicationBuilder UseRouting(this IApplicationBuilder builder)
        {

            if (builder == null)
            {
                throw new ArgumentNullException(nameof(builder));
            }

            //在调用UseEndpoint之前验证AddRouting服务是否已完成
　　　　　　  //我们使用RoutingMarkerService来确保是否添加了所有服务。
 　　　　　　 //AddRouting服务在Program类的ConfigureWebHostDefaults调用后添加。


            VerifyRoutingServicesAreRegistered(builder);

            //VerifyRoutingServicesAreRegistered 内部
            //if (app.ApplicationServices.GetService(typeof(RoutingMarkerService)) == null)
            //{
            //    throw new InvalidOperationException(Resources.FormatUnableToFindServices(
            //        nameof(IServiceCollection),
            //        nameof(RoutingServiceCollectionExtensions.AddRouting),
            //        "ConfigureServices(...)"));
            //}

            //初始化数据源
            var endpointRouteBuilder = new DefaultEndpointRouteBuilder(builder);

            //DefaultEndpointRouteBuilder构造类内部
            //public DefaultEndpointRouteBuilder(IApplicationBuilder applicationBuilder)
            //{
            //    ApplicationBuilder = applicationBuilder ?? throw new ArgumentNullException(nameof(applicationBuilder));
            //    DataSources = new List<EndpointDataSource>();
            //}


            //EndpointRouteBuilder为字符串常量 __EndpointRouteBuilder
            //// builder.Properties["__EndpointRouteBuilder"] = endpointRouteBuilder;
            builder.Properties[EndpointRouteBuilder] = endpointRouteBuilder;

            //操作完成后对此实例引用
            return builder.UseMiddleware<EndpointRoutingMiddleware>(endpointRouteBuilder);
        }

UseEndpoints内部：

   public static IApplicationBuilder UseEndpoints(this IApplicationBuilder builder, Action<IEndpointRouteBuilder> configure)
        {
            if (builder == null)
            {
                throw new ArgumentNullException(nameof(builder));
            }

            if (configure == null)
            {
                throw new ArgumentNullException(nameof(configure));
            }

            
            //在调用UseEndpoint之前验证AddRouting服务是否已完成
　　　　　　　//我们使用RoutingMarkerService来确保是否添加了所有服务。
 　　　　　　 //AddRouting服务在Program类的ConfigureWebHostDefaults调用后添加。


            //所以在调用UseEndpoint之前 必须要先调用UseRouting，否则报错。
            VerifyRoutingServicesAreRegistered(builder);

            //VerifyRoutingServicesAreRegistered方法内部
            //private static void VerifyRoutingServicesAreRegistered(IApplicationBuilder app)
            //{
            //    if (app.ApplicationServices.GetService(typeof(RoutingMarkerService)) == null)
            //    {
            //        throw new InvalidOperationException(Resources.FormatUnableToFindServices(
            //            nameof(IServiceCollection),
            //            nameof(RoutingServiceCollectionExtensions.AddRouting),
            //            "ConfigureServices(...)"));
            //    }
            //}

            //验证端点路由中间件是否已注册
            VerifyEndpointRoutingMiddlewareIsRegistered(builder, out var endpointRouteBuilder);

            //VerifyEndpointRoutingMiddlewareIsRegistered方法内部
            //private static void VerifyEndpointRoutingMiddlewareIsRegistered(IApplicationBuilder app, out DefaultEndpointRouteBuilder endpointRouteBuilder)
            //{
            //    if (!app.Properties.TryGetValue(EndpointRouteBuilder, out var obj))
            //    {
            //        var message =
            //            $"{nameof(EndpointRoutingMiddleware)} matches endpoints setup by {nameof(EndpointMiddleware)} and so must be added to the request " +
            //            $"execution pipeline before {nameof(EndpointMiddleware)}. " +
            //            $"Please add {nameof(EndpointRoutingMiddleware)} by calling '{nameof(IApplicationBuilder)}.{nameof(UseRouting)}' inside the call " +
            //            $"to 'Configure(...)' in the application startup code.";
            //        throw new InvalidOperationException(message);
            //    }

            //    //如果此处转换失败，程序会出错。
            //    endpointRouteBuilder = (DefaultEndpointRouteBuilder)obj;

            //    
            //    //此检查处理在两者之间调用Map或其他分叉管道的情况
            //    if (!object.ReferenceEquals(app, endpointRouteBuilder.ApplicationBuilder))
            //    {
            //        var message =
            //            $"The {nameof(EndpointRoutingMiddleware)} and {nameof(EndpointMiddleware)} must be added to the same {nameof(IApplicationBuilder)} instance. " +
            //            $"To use Endpoint Routing with 'Map(...)', make sure to call '{nameof(IApplicationBuilder)}.{nameof(UseRouting)}' before " +
            //            $"'{nameof(IApplicationBuilder)}.{nameof(UseEndpoints)}' for each branch of the middleware pipeline.";
            //        throw new InvalidOperationException(message);
            //    }
            //}


            configure(endpointRouteBuilder);

            //我们正在将数据源注册到一个全局集合中
            //可用于发现端点或生成URL。
            //每个中间件都有自己的数据源集合，所有这些数据源也
            //被添加到全局集合中。
            var routeOptions = builder.ApplicationServices.GetRequiredService<IOptions<RouteOptions>>();
            foreach (var dataSource in endpointRouteBuilder.DataSources)
            {
                routeOptions.Value.EndpointDataSources.Add(dataSource);
            }

            //操作完成后对此实例引用
            return builder.UseMiddleware<EndpointMiddleware>();
        }