Question

我正在为背景工作者创建一个UrlHelper来创建回调网址，这意味着它不是正常请求的一部分，我可以通过DI请求它。

在ASP.Net 5中，我可以创建一个HttpRequest并为它提供与构建我的应用程序相同的HttpConfiguration，但在ASP.Net Core 2.0中，UrlHelper依赖于一个完整的ActionContext，这有点难以制作。 / p>

我有一个工作原型，但是它使用了一个讨厌的黑客来将路线数据走私到应用程序启动过程之外。有更好的方法吗？

public class Capture
{
    public IRouter Router { get; set; }
}

public static class Ext
{
    // Step 1: Inject smuggler when building web host
    public static IWebHostBuilder SniffRouteData(this IWebHostBuilder builder)
    {
        return builder.ConfigureServices(svc => svc.AddSingleton<Capture>());
    }

    // Step 2: Swipe the route data in application startup
    public static IApplicationBuilder UseMvcAndSniffRoutes(this IApplicationBuilder app)
    {
        var capture = app.ApplicationServices.GetRequiredService<Capture>();
        IRouteBuilder capturedRoutes = null;
        app.UseMvc(routeBuilder => capturedRoutes = routeBuilder);
        capture.Router = capturedRoutes?.Build();
        return app;
    }

    // Step 3: Build the UrlHelper using the captured routes and webhost
    public static IUrlHelper GetStaticUrlHelper(this IWebHost host, string baseUri)
        => GetStaticUrlHelper(host, new Uri(baseUri));
    public static IUrlHelper GetStaticUrlHelper(this IWebHost host, Uri baseUri)
    {
        HttpContext httpContext = new DefaultHttpContext()
        {
            RequestServices = host.Services,
            Request =
                {
                    Scheme = baseUri.Scheme,
                    Host = HostString.FromUriComponent(baseUri),
                    PathBase = PathString.FromUriComponent(baseUri),
                },
        };

        var captured = host.Services.GetRequiredService<Capture>();
        var actionContext = new ActionContext
        {
            HttpContext = httpContext,
            RouteData = new RouteData { Routers = { captured.Router }},
            ActionDescriptor = new ActionDescriptor(),
        };
        return new UrlHelper(actionContext);
    }
}

// Based on dotnet new webapi

public class Program
{
    public static void Main(string[] args)
    {
        BuildWebHost(args);//.Run();
    }

    public static IWebHost BuildWebHost(string[] args)
    {
        var captured = new Capture();
        var webhost = WebHost.CreateDefaultBuilder(args)
            .SniffRouteData()
            .UseStartup<Startup>()
            .Build();

        var urlHelper = webhost.GetStaticUrlHelper("https://my.internal.service:48923/somepath");
        Console.WriteLine("YO! " + urlHelper.Link(nameof(ValuesController), null));
        return webhost;
    }
}

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc();
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env, Capture capture)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseMvcAndSniffRoutes();
    }
}

[Route("api/[controller]", Name = nameof(ValuesController))]
public class ValuesController : Controller
{
    // GET api/values
    [HttpGet]
    public IEnumerable<string> Get()
    {
        return new string[] { "value1", "value2" };
    }

    // etc
}

Answer 1

浏览源代码似乎没有那么糟糕的解决方案。

在UseMvc（）方法中，正在构建的IRouter对象是passed to the RouterMiddleware，stores it in a private field并仅将其公开给请求。所以反射将是你唯一的另一种选择，显然是在运行之外。

但是，如果您需要使用IUrlHelper.Content（）仅生成静态路径，则您不需要将路由器作为default implementation won't use it。在这种情况下，您可以像这样创建帮助程序：

var actionContext = new ActionContext(httpContext, new RouteData(), new ActionDescriptor());
var urlHelper = new UrlHelper(actionContext);

Answer 2

使用ASP.NET Core 2.2 releasing today，他们添加了一个LinkGenerator类，听起来像它将解决此问题（tests看起来很有希望）。我很想尝试一下，但是由于我目前没有积极参与需要该项目的项目，因此它需要稍等一下。但是我很乐观地将其标记为新答案。

ASP.Net Core 2.0：无需请求即可创建UrlHelper

2 个答案: