How to access RouteData from an ASP.Net 5 Tag Helper in MVC 6

Question

I am trying to get hold of the current route so that I can highlight the active page in a set of links using a Tag Helper.

The TagHelperContext doesn't give me access to anything useful. How can I get a reference to the RouteData?

Mantooth

Answer 1

I eventually found the answer described here: https://github.com/aspnet/Announcements/issues/28

You can import the ViewContext using property injection by using a new attribute. You need to create a property in you tag helper class like this:

[ViewContext]
public ViewContext ViewContext { get; set; }

You can then access the current controller or action like so:

var pageController = ViewContext.RouteData.Values["controller"];
var pageAction = ViewContext.RouteData.Values["action"];

Maybe I posted this question before doing enough research, but this was not entirely obvious, so I hope this helps someone else!

Mantooth

the way I've been doing it is to pass in those things as attributes to my taghelper the same way Microsoft does it for AnchorTagHelper ie asp-controller and asp-action so that the consumer of my taghelper can specify it rather than assuming to use the same as the current request. – Annunciata

Thanks Joe - just to clarify, I am doing this too. I am comparing what is in the route data to the asp-controller and asp-action to see if the link in question is currently active. i.e highlight in the menu. So if this is a shared razor view you cannot pass in the currently active one, it has to be dynamic. Hope that makes sense. – Mantooth

@Joe - also, out of interest are you naming them asp-controller or just controller? I'm not sure if I should be using the asp- prefix or not. I raised #32533234 but it's been put on hold unfortunately (for inciting a religious war or something about opinions) – Mantooth

I used asp-controller and asp-action to be consistent with the same attributes on anchortaghelper but for all my other attributes I'm using a custom prefix. – Annunciata