在中间件中获取 UrlHelper asp.net mvc core 2.0

Question

如何获取中间件中的UrlHelper。我尝试如下但 actionContextAccessor.ActionContext return null.

public void ConfigureServices(IServiceCollection services)
{
    services.AddSession();

    services
        .AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
        .AddCookie();

    services.AddMvc();
    services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseSession();

    if (env.IsDevelopment())
    {
        app.UseBrowserLink();
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseExceptionHandler("/Home/Error");
    }

    app.UseStaticFiles();
    app.UseAuthentication();
    app.Use(async (context, next) =>
    {
        var urlHelperFactory = context.RequestServices.GetService<IUrlHelperFactory>();
        var actionContextAccessor = context.RequestServices.GetService<IActionContextAccessor>();

        var urlHelper = urlHelperFactory.GetUrlHelper(actionContextAccessor.ActionContext);
        await next();
        // Do logging or other work that doesn't write to the Response.
    });

    app.UseMvc(routes =>
    {
        routes.MapRoute(
            name: "default",
            template: "{controller=Home}/{action=Index}/{id?}");
    });
}

Answer 1

您可以尝试将其添加到 ConfigureServices(IServiceCollection services) 上的服务容器中。您可以像下面这样操作：

 public IServiceProvider ConfigureServices(IServiceCollection services) {
    //Service injection and setup
    services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();
                services.AddScoped<IUrlHelper>(factory =>
                {
                    var actionContext = factory.GetService<IActionContextAccessor>()
                                               .ActionContext;
                    return new UrlHelper(actionContext);
                });

    //....

   // Build the intermediate service provider then return it
    return services.BuildServiceProvider();
}

然后你可以修改你的 Configure() 方法来接收 IServiceProvider ，你可以通过执行以下操作获得 UrlHelper 的实例。

public void Configure(IApplicationBuilder app, IServiceProvider serviceProvider) {

    //Code removed for brevity

    var urlHelper = serviceProvider.GetService<IUrlHelper>(); <-- helper instance

    app.UseMvc();
}

注意：将其放在services.Mvc()

之后

Answer 2

您的应用中有 2 个管道。您要连接的 ASP.NET 核心管道。以及由 UseMvc 设置的 ASP.NET MVC 管道。 ActionContext 是一个 MVC 概念，这就是它在 ASP.NET 核心管道中不可用的原因。要连接到 MVC 管道，您可以使用过滤器：https://docs.microsoft.com/en-us/aspnet/core/mvc/controllers/filters

编辑：修复了link文章

在中间件中获取 UrlHelper asp.net mvc core 2.0

Get UrlHelper in middleware asp.net mvc core 2.0

c#

dependency-injection

middleware

asp.net-core-mvc-2.0