how do I add a url parameter to a routelink in asp.net mvc?

Question

All, my situation is that I have the basic route, plus some other simple routes:

routes.MapRoute(
                "Default",                                              
                "{controller}/{action}/{id}",                           
                new { controller = "Home", action = "Index", id = 1}
            );

So the following url works: http://somesite.com/tags/index/1

However, some of my index pages take url parameters in the following fashion:

http://somesite.com/tags/index/1?when=lastmonth

How do I use Html.RouteLink to link to this?

You can't add '?' to routes in the global asax file like this:

routes.MapRoute("TagsWhen", "Tags/index/{id}?when={when}",
      new {controller = "Tags", action = "Index", id = "", when = ""});

If this route worked I could link to it using:

Html.RouteLink(string.Format("{0} ", link.Rating), "LinksWhen", 
               new {id=link.ReferenceId, when=Model.When})

but it doesn't! So I'm not sure how I would use a Html.RouteLink to generate http://somesite.com/tags/index/1?when=lastmonth

Answer 1

I don't have a computer able to test this, but off the top of my head

<%= Html.ActionLink("Link text", "Index", "Home", new { id = 1, when = "lastmonth" } %>

You don't need to specify optional parameters in your routes in the global.asax.cs file. Anything that doesn't match gets chucked into the query string by default.

Answer 2

Just found the solution myself. You can just do a regular Html.RouteLink and any object properties you don't have mapped to the url in global.asax it adds as a url parameter.

So using this route:

    routes.MapRoute(
        "Links",                                              
        "Links/details/{id}",                           
        new { controller = "Links", action = "Details", id = ""} defaults
    );

and this routelink:

Html.RouteLink("Link Text", "Links", 
        new {id=link.ReferenceId, when=Model.When })

generates the correct url:

http://localhost:2535/Links/details/1?when=onemonth

Answer 3

Matthew's approach probably didn't work because he needed another null parameter on the end, otherwise it passes the route values as html attributes. :)

<%= Html.ActionLink("Link text", "Index", "Home", new { id = 1, when = "lastmonth" }, null) %>

That last MapRoute() you came up with should work fine against it.