ASP.NET MVC Core IUrlHelper: Convert Your UrlHelper Extensions

When converting your MVC application over to MVC Core, you want to reuse as much as possible. Today, I show you a simple little trick on how to continue using your existing URLHelpers in ASP.NET MVC Core.

March 6th, 2017 • MVC •
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Almost 10 years ago, ASP.NET MVC was introduced and developers started learning a new way to maximize web development using something other than Web Forms.

Ten years later, We are now introduced to ASP.NET Core along with a new MVC.

Essentially, the methodology is the same, but we have new plumbing in the system.

ASP.NET was completely rewritten from the ground up.

Things like everything being dependency injected, a new way to configure your application called Middleware, and TagHelpers to remove those pesky HtmlHelpers.

So after building a couple TagHelpers and tinkering with some custom Middleware almost a year ago, I thought this would be a great time to continue learning about ASP.NET MVC Core and truly how different it is compared to the earlier versions.

I started with something simple: UrlHelpers.

It's hardly a collection because it's so application-specific, but I thought it would be easy to move them into MVC Core.

Manage Your Links

When I first started learning about ASP.NET MVC, I was working on a couple of projects and was always using Url.Action() in my Views.

The project had a total of over 50 pages and it continued to grow.

One day, the founder wanted to change the URL and make it more search-engine-friendly.

I had to change over 50 pages of Url.Action() in my Views.

There had to be a better way to build these URLs in every single page.

So I started creating Url Catalogs.

Everything was fine...until ASP.NET MVC Core.

Did Links Just Get Complicated?

I was wondering why my UrlHelper Extension Methods weren't working when I started receiving compiler errors.

After looking around for hints on how to use UrlHelpers in ASP.NET MVC Core controllers, I came across a lot of Stack Overflow entries on creating an IUrlHelperFactory, then the factory would get a UrlHelper, then the UrlHelper would...

Sheesh.

Isn't there just a UrlHelper class anymore?

I know it can be injected, but wow, I just want to piggy-back off an existing UrlHelper.

I looked into the Controller class and yes, there was a Url property type of IUrlHelper.

Solving the problem with One Letter

So basically, I needed to attach my extension methods to a IUrlHelper instead of a UrlHelper.

After digging, I discovered something magical (like unicorns-magical) about extension methods.

You can use extension methods to extend a class or interface

Mind. Blown.

In my catalog of Url Helpers, my extensions went from this:

public static string RootUrl(this UrlHelper helper)
{
    return helper.Content("~/");
}

to this:

public static string RootUrl(this IUrlHelper helper)
{
    return helper.Content("~/");
}

with no issues.

Yeah, I'm completely satisfied with this solution. :-)

With the way I create my ViewModels, I always pass along a ControllerContext which contains the Controller which contains a Url.

As before, I will always have site-wide access to my links.

Conclusion

After playing around with UrlHelpers this weekend, I can finally say I know where to hit now that I've made it out of those weeds.

These UrlHelper catalogs definitely provide an easy (and magic-string free) way to create site-wide links for Views and Controllers.

Stay tuned for more.

Did this make sense? Did you create your Urls a different way? Post your comments below and let's discuss.

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Picture of Jonathan Danylko

Jonathan Danylko is a freelance web architect and avid programmer who has been programming for over 20 years. He has developed various systems in numerous industries including e-commerce, biotechnology, real estate, health, insurance, and utility companies.

When asked what he likes to do in his spare time, he replies, "Programming."

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