MVC ActionLink add all (optional) parameters from current url

The very famous ActionLink:

 <%: Html.ActionLink("Back to List", "Index")%>

Now, this link is in my Details view. The Index view is a search page. The URL of that looks like this:

http://localhost:50152/2011-2012/Instelling/Details/76?gemeente=Dendermonde&postcode=92**&gebruikerscode=VVKSO114421&dossiernr=114421%20&organisatie=CLB

As you can see, quite the amount of parameters. Obviously I want to keep all these parameters when I return to the Index page, so I need to add them in the ActionLink.

Now, I'm tired of doing that manually, it's ok for 1, but not for 6. This should go a lot easier.

Question: How do I return All parameters of the current URL into the ActionLink as optional RouteValues.

I've been looking to Request.QueryString. It has to be something with that. I was thinking of writing some static method in Global.asax doing the job but no luck yet. Maybe there is an easy way to do this which I don't know about?

Edit: This is what I came up with (which works)

In global.asax:

    public static RouteValueDictionary optionalParamters(NameValueCollection c) {
        RouteValueDictionary r = new RouteValueDictionary();
        foreach (string s in c.AllKeys) {
            r.Add(s, c[s]);
        }
        return r;
    }

Details.aspx:

    <%: Html.ActionLink("Back to List", "Index", MVC2_NASTEST.MvcApplication.optionalParamters(Request.QueryString))%>

Where do I best put this code? not in Global.asax I guess...

Edit 2:

using System;
using System.Web.Mvc;

namespace MVC2_NASTEST.Helpers {
    public static class ActionLinkwParamsExtensions {
        public static MvcHtmlString CustomLink(this HtmlHelper helper, string linktext) {
            //here u can use helper to get View context and then routvalue dictionary
            var routevals = helper.ViewContext.RouteData.Values;
            //here u can do whatever u want with route values
            return null;
        }

    }
}


<%@ Import Namespace="MVC2_NASTEST.Helpers" %>
...
<%: Html.ActionLinkwParams("Index") %>