Injection of IUrlHelper in ASP.NET Core

Question

In RC1 , IUrlHelper could be injected in services (with services.AddMvc() in startup class)

This doesn't work anymore in RC2 . Does anybody know how to do it in RC2 as just newing up a UrlHelper requires an ActionContext object. Don't know how to get that outside a controller.

Answer 1

.NET Core 3+ and .NET 5 Update (2020 and later)

Use LinkGenerator as detailed in @Dmitry Pavlov's answer on this thread . It's injectable as part of the web framework, and works with the HttpContext already available in controllers, or accessible in other services by injecting the IHttpContextAccessor .

For ASP.NET Core RC2 there is an issue for this on the github repo . Instead of injecting the IUrlHelper , take an IUrlHelperFactory . It also sounds like you'd need the IActionContextAccessor injected as a Controller no longer has a public property ActionContext .

Register the dependency:

services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();

Then depend on it:

public SomeService(IUrlHelperFactory urlHelperFactory,
                   IActionContextAccessor actionContextAccessor)
{
 
    var urlHelper =
        urlHelperFactory.GetUrlHelper(actionContextAccessor.ActionContext);
}

Then use it as you see fit.

Answer 2

For ASP.NET Core 3.x app just inject IHttpContextAccessor and LinkGenerator to your controller or service. They should be already available in DI .

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Routing;

namespace Coding-Machine.NET
{
    public class MyService
    {
        private readonly IHttpContextAccessor _accessor;
        private readonly LinkGenerator _generator;

        public MyService(IHttpContextAccessor accessor, LinkGenerator generator)
        {
            _accessor = accessor;
            _generator = generator;
        }

        private string GenerateConfirmEmailLink()
        {
            var callbackLink = _generator.GetUriByPage(_accessor.HttpContext,
                page: "/Account/ConfirmEmail",
                handler: null, 
                values: new {area = "Identity", userId = 123, code = "ASDF1234"});

            return callbackLink;
        }
    }
}

If your app can't resolve IHttpContextAccessor just add this to DI :

public void ConfigureServices(IServiceCollection services)
{
     services.AddHttpContextAccessor();
}

Answer 3

For Net Core 2.0

Add this after service.AddMvc()

services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();
services.AddScoped<IUrlHelper>(factory =>
{
    var actionContext = factory.GetService<IActionContextAccessor>()
                                   .ActionContext;
    return new UrlHelper(actionContext);
});

Answer 4

For .Net Core 2.0

services.AddMvc();

services.AddScoped<IUrlHelper>(x =>
{
   var actionContext = x.GetRequiredService<IActionContextAccessor>().ActionContext;
   var factory = x.GetRequiredService<IUrlHelperFactory>();
   return factory.GetUrlHelper(actionContext);
});

Answer 5

ASP.NET Core 2.0

Install

PM> Install-Package AspNetCore.IServiceCollection.AddIUrlHelper

Use

public void ConfigureServices(IServiceCollection services)
{
   ... 
   services.AddUrlHelper();
   ... 
}

Disclaimer: author of this package

Answer 6

For ASP.Net Core 2.0 you must not inject an IUrlHelper. It's available as a property of the controller. ControllerBase.Url is an IUrlHelper instance.