ترتيب الوسطاء وحدود الأخطاء

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;

using var services = new ServiceCollection().BuildServiceProvider();
var builder = new ApplicationBuilder(services);
var trace = new List<string>();
builder.Use(next => async context => { trace.Add("outer-before"); await next(context); trace.Add("outer-after"); });
builder.Use(next => async context => { trace.Add("inner-before"); await next(context); trace.Add("inner-after"); });
builder.Run(context => { trace.Add("terminal"); return Task.CompletedTask; });
await builder.Build()(new DefaultHttpContext());
Console.WriteLine(string.Join(">", trace));

outer-before>inner-before>terminal>inner-after>outer-after

ينفذ المفوض الطرفي بين مراحل العمل السابق ومراحل العمل اللاحق المعكوسة؛ ولا يفتح مستمع HTTP.

using System;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;

bool maintenance = true;
bool applicationRan = false;
RequestDelegate application = context => { applicationRan = true; return Task.CompletedTask; };
RequestDelegate gate = async context =>
{
    if (maintenance) { context.Response.StatusCode = StatusCodes.Status503ServiceUnavailable; return; }
    await application(context);
};
var context = new DefaultHttpContext();
await gate(context);
Console.WriteLine($"status={context.Response.StatusCode} applicationRan={applicationRan}");

status=503 applicationRan=False

يعيد العلم المحلي حالة 503 قبل تنفيذ مفوض التطبيق.