Generate URL in HTML helper

Question

Normally in an ASP.NET view one could use the following function to obtain a URL (not an <a>):

Url.Action("Action", "Controller");

However, I cannot find how to do it from a custom HTML helper. I have

public class MyCustomHelper
{
   public static string ExtensionMethod(this HtmlHelper helper)
   {
   }
}

The helper variable has the Action and GenerateLink methods, but they generate <a>’s. I did some digging in the ASP.NET MVC source code, but I could not find a straightforward way.

The problem is that the Url above is a member of the view class and for its instantiation it needs some contexts and route maps (which I don’t want to be dealing with and I’m not supposed to anyway). Alternatively, the instance of the HtmlHelper class has also some context which I assume is either supper of subset of the context information of the Url instance (but again I don’t want to dealing with it).

In summary, I think it is possible but since all ways I could see, involve some manipulation with some more or less internal ASP.NET stuff, I wonder whether there is a better way.

Edit: For instance, one possibility I see would be:

public class MyCustomHelper
{
    public static string ExtensionMethod(this HtmlHelper helper)
    {
        UrlHelper urlHelper = new UrlHelper(helper.ViewContext.RequestContext);
        urlHelper.Action("Action", "Controller");
    }
}

But it does not seem right. I don't want to be dealing with instances of UrlHelper myself. There must be an easier way.

I realize this is a simplified example, but for the example shown I would extend UrlHelper instead of HtmlHelper. Your real code may need both, though. — Craig Stuntz, Sep 18 '09 at 12:55
Sorry, I should have been more clear: I wanted to do some HTML rendeting in the extension method and I needed to generate URL's for it. — Jan Zich, Sep 18 '09 at 13:49

score 220 · Accepted Answer · answered Sep 18 '09 at 10:27

220

You can create url helper like this inside html helper extension method:

var urlHelper = new UrlHelper(htmlHelper.ViewContext.RequestContext);
var url = urlHelper.Action("Home", "Index")

answered Sep 18 '09 at 10:27

Darin Dimitrov

1,023,142
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2

I think that it would be better if constructor also initialize RouteCollection `new UrlHelper(htmlHelper.ViewContext.RequestContext, htmlHelper.RouteCollection)` – kpull1 Sep 23 '15 at 07:33

score 22 · Answer 2 · answered Jan 24 '13 at 10:20

22

You can also get links using UrlHelper public and static class:

UrlHelper.GenerateUrl(null, actionName, controllerName, null, null, null, routeValues, htmlHelper.RouteCollection, htmlHelper.ViewContext.RequestContext, true)

In this example you don't have to create new UrlHelper class what could be a little advantage.

answered Jan 24 '13 at 10:20

cryss

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I like this answer more because sets the RouteCollection. – kpull1 Sep 23 '15 at 07:32

score 10 · Answer 3 · answered May 29 '13 at 11:13

Here is my tiny extenstion method for getting UrlHelper of a HtmlHelper instance :

  public static partial class UrlHelperExtensions
    {
        /// <summary>
        /// Gets UrlHelper for the HtmlHelper.
        /// </summary>
        /// <param name="htmlHelper">The HTML helper.</param>
        /// <returns></returns>
        public static UrlHelper UrlHelper(this HtmlHelper htmlHelper)
        {
            if (htmlHelper.ViewContext.Controller is Controller)
                return ((Controller)htmlHelper.ViewContext.Controller).Url;

            const string itemKey = "HtmlHelper_UrlHelper";

            if (htmlHelper.ViewContext.HttpContext.Items[itemKey] == null)
                htmlHelper.ViewContext.HttpContext.Items[itemKey] = new UrlHelper(htmlHelper.ViewContext.RequestContext, htmlHelper.RouteCollection);

            return (UrlHelper)htmlHelper.ViewContext.HttpContext.Items[itemKey];
        }
    }

Use it as:

public static MvcHtmlString RenderManagePrintLink(this HtmlHelper helper, )
{    
    var url = htmlHelper.UrlHelper().RouteUrl('routeName');
    //...
}

(I'm posting this ans for reference only)

Excellent approach because it reuses an existing object rather than creating a new one. — Mike, Mar 11 '17 at 05:04
We are using ASP.NET 4.5 and were experiencing re-entrancy issues. We don't believe UrlHelper is reusable across http requests. Please take notice. — Carl in 't Veld, Jul 02 '18 at 15:58

Generate URL in HTML helper

3 Answers3

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