Question

I have a partial view for displaying a list of items, I use this partial view in several different places. Inside this partial view I use a paginator –

@Html.PagedListPager(Model, page => Url.Action(null, new { page = page }))

This results in the paginator showing page urls for whatever Action and View i’m already looking at.

Problem is, on my search page I use a query string for the search string, and the Url.Action method does not include existing querystring parameters.

Instead of /Search?s=bla&page=3 I end up with /Search?page=3

How can I generate a url using the existing query string?

Edit:

Here is my code

    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");


        routes.Add(
        "Search",
        new SearchRoute("Search", new MvcRouteHandler())
        {
            Defaults = new RouteValueDictionary(
                new { controller = "Search", action = "Index" })
        }); 


        routes.MapRoute(
            "Default",
            "{controller}/{action}/{id}",
            new { controller = "Call", action = "Index", id = UrlParameter.Optional }


        );



    }

    public class SearchRoute : Route
    {
        public SearchRoute(string url, IRouteHandler routeHandler)
            : base(url, routeHandler)
        {
        }

        public override VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values)
        {

            System.Diagnostics.Debug.WriteLine(Url);

            if (HttpContext.Current != null)
            {

                string s = HttpContext.Current.Request.QueryString["s"];

                if (!string.IsNullOrEmpty(s))
                    values.Add("s", s);

            }

            return base.GetVirtualPath(requestContext, values);
        }
    }

Answer 1

Using a custom route, you can preserve the query string because most Url generation logic uses the route to generate the URL. In this case I am checking the Request object for a query string called XXX and adding it into the route if it exists, you can make it more generic if you like.

using System.Web;
using System.Web.Routing;

public class PreserveQueryStringRoute : Route
{
    public PreserveQueryStringRoute(string url, IRouteHandler routeHandler)
        : base(url, routeHandler)
    {
    }

    public override VirtualPathData GetVirtualPath(RequestContext requestContext, RouteValueDictionary values)
    {
        if(HttpContext.Current != null)
        {
            values = new RouteValueDictionary(values);   //this is the bug fix!

            if (!string.IsNullOrEmpty(HttpContext.Current.Request.QueryString["XXX"]))
                values.Add("XXX", HttpContext.Current.Request.QueryString["XXX"]);

        }

        var path = base.GetVirtualPath(requestContext, values);
        return path;
    }
}

Register the route as per normal in the global.ascx (though probably not for such a generic match as I have below)

        routes.Add(
            "Default",
            new PreserveQueryStringRoute("{controller}/{action}/{id}", new MvcRouteHandler())
            {
                Defaults = new RouteValueDictionary(
                    new { controller = "Home", action = "Index", id = UrlParameter.Optional })
            });   

Edit:

Ok, here’s an update.. its a bug fix, and an example of how to register the route (See corrected code above for bug fix)

Here’s how to register it:

    routes.Add(      
    "Search",      
    new SearchRoute("Search", new MvcRouteHandler())      
    {      
        Constraints = new RouteValueDictionary(      
            new { controller = "Search", action = "Index" })      
    });