Call UrlHelper in models in ASP.NET MVC

Question

Helpful tip, in any ASP.NET application, you can get a reference of the current HttpContext

HttpContext.Current

which is derived from System.Web. Therefore, the following will work anywhere in an ASP.NET MVC application:

UrlHelper url = new UrlHelper(HttpContext.Current.Request.RequestContext);
url.Action("ContactUs"); // Will output the proper link according to routing info

Example:

public class MyModel
{
    public int ID { get; private set; }
    public string Link
    {
        get
        {
            UrlHelper url = new UrlHelper(HttpContext.Current.Request.RequestContext);
            return url.Action("ViewAction", "MyModelController", new { id = this.ID });
        }
    }

    public MyModel(int id)
    {
        this.ID = id;
    }
}

Calling the Link property on a created MyModel object will return the valid Url to view the Model based on the routing in Global.asax

I like Omar's answer but that's not working for me. Just for the record this is the solution I'm using now:

var httpContext = HttpContext.Current;

if (httpContext == null) {
  var request = new HttpRequest("/", "http://example.com", "");
  var response = new HttpResponse(new StringWriter());
  httpContext = new HttpContext(request, response);
}

var httpContextBase = new HttpContextWrapper(httpContext);
var routeData = new RouteData();
var requestContext = new RequestContext(httpContextBase, routeData);

return new UrlHelper(requestContext);

A UrlHelper can be constructed from within a Controller action with the following:

 var url = new UrlHelper(this.ControllerContext.RequestContext);
 url.Action(...);

Outside of a controller, a UrlHelper can be constructed by creating a RequestContext from the RouteTable.Routes RouteData.

HttpContextWrapper httpContextWrapper = new HttpContextWrapper(System.Web.HttpContext.Current);
UrlHelper urlHelper = new UrlHelper(new RequestContext(httpContextWrapper, RouteTable.Routes.GetRouteData(httpContextWrapper)));

(Based on Brian's answer, with a minor code correction added.)

Yes, you can instantiate it. You can do something like:

var ctx = new HttpContextWrapper(HttpContext.Current);
UrlHelper helper = new UrlHelper(
   new RequestContext(ctx,
   RouteTable.Routes.GetRouteData(ctx));

RouteTable.Routes is a static property, so you should be OK there; to get a HttpContextBase reference, HttpContextWrapper takes a reference to HttpContext, and HttpContext delivers that.

After trying all the other answers, I ended up with

$"/api/Things/Action/{id}"

Haters gonna hate ¯\_(ツ)_/¯