ASP.NET 5 Tips: UrlHelper

ASPNET Core TagHelpers.

Posted by Devon Burriss on January 18, 2016

Note that this is specific to the upcoming RC 2 using the dotnet CLI. Currently in RC 1 this is not an issue.

So I was messing around with David Fowl's repository that makes use of the new RC 2 bits that run on the new dotnet CLI.

Everything was fine until I tried to create a TagHelper that makes use of IUrlHelper. In RC 1 IUrlHelper is registered automatically with the DI system but apparently not in RC 2. After much searching I found the following commit which explained the change.

So what follows is how I got an IUrlHelper into my TagHelper.

It seems we should instead make use of IUrlHelperFactory to get an instance of IUrlHelper.

In Startup.cs service configuration I register IActionContextAccessor and IUrlHelperFactory:

public void ConfigureServices(IServiceCollection services)

Then I inject IUrlHelperFactory into the TagHelper constructor and use the factory to create a new instance of a IUrlHelper:

public class EmailTagHelper : TagHelper
  private readonly IUrlHelper _urlHelper;

  public EmailTagHelper(IUrlHelperFactory urlHelperFactory, IActionContextAccessor actionContextAccessor)
  	_urlHelper = urlHelperFactory.GetUrlHelper(actionContextAccessor.ActionContext);
  //process override here

I am guessing that this article will only be useful next month when RC 2 hits but it was great to see what is coming. I am quite liking the new CLI and with a bit of digging I have managed to get most things working, so the team seems to be making great progress toward RC 2. Please let me know below if you found this useful... or if things change :)

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