Question

I’m implementing a faceted search functionality where the user can filter and drill down on 4 properties of my model: City, Type, Purpose and Value.

I have a view section with the facets like this:

Each line displayed in the above image is clickable so that the user can drill down and do the filtering…

The way I’m doing it is with query strings that I pass using a custom ActionLink helper method:

 @Html.ActionLinkWithQueryString(linkText, "Filter",
                                 new { facet2 = Model.Types.Key, value2 = fv.Range });

This custom helper keeps the previous filters (query string parameters) and merges them with new route values present in other action links. I get a result like this when the user has applied 3 filters:

http://leniel-pc:8083/realty/filter?facet1=City&value1=Volta%20Redonda&
facet2=Type&value2=6&facet3=Purpose&value3=3

It’s working but I’d like to know about a better/cleaner way of doing this using routes. The order of the parameters can change depending on the filters the user has applied. I have something like this in mind:

http://leniel-pc:8083/realty/filter // returns ALL rows

http://leniel-pc:8083/realty/filter/city/rio-de-janeiro/type/6/value/50000-100000

http://leniel-pc:8083/realty/filter/city/volta-redonda/type/6/purpose/3

http://leniel-pc:8083/realty/filter/type/7/purpose/1

http://leniel-pc:8083/realty/filter/purpose/3/type/4

http://leniel-pc:8083/realty/filter/type/8/city/carangola

Is this possible? Any ideas?

Answer 1

Is this possible? Any ideas?

I would keep the query string parameters for filtering.

But if you wanted to achieve the urls you have asked for in your question I will cover 2 possible techniques.

For both approaches that I will present here I assume that you already have a view model:

public class FilterViewModel
{
    public string Key { get; set; }
    public string Value { get; set; }
}

and a controller:

public class RealtyController : Controller
{
    public ActionResult Filter(IEnumerable<FilterViewModel> filters)
    {
        ... do the filtering ...
    }
}

---

The first option is to write a custom model binder that will be associated with the IEnumerable<FilterViewModel> type:

public class FilterViewModelBinder : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var filtersValue = bindingContext.ValueProvider.GetValue("pathInfo");
        if (filtersValue == null || string.IsNullOrEmpty(filtersValue.AttemptedValue))
        {
            return Enumerable.Empty<FilterViewModel>();
        }

        var filters = filtersValue.AttemptedValue;
        var tokens = filters.Split('/');
        if (tokens.Length % 2 != 0)
        {
            throw new Exception("Invalid filter format");
        }

        var result = new List<FilterViewModel>();
        for (int i = 0; i < tokens.Length - 1; i += 2)
        {
            var key = tokens[i];
            var value = tokens[i + 1];
            result.Add(new FilterViewModel
            {
                Key = tokens[i],
                Value = tokens[i + 1]
            });
        }

        return result;
    }
}

which will be registered in Application_Start:

ModelBinders.Binders.Add(typeof(IEnumerable<FilterViewModel>), new FilterViewModelBinder());

and you will also have a filter route:

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

    routes.MapRoute(
        "Filter",
        "realty/filter/{*pathInfo}",
        new { controller = "Realty", action = "Filter" }
    );

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

---

A second possibility is to write a custom route

public class FilterRoute : Route
{
    public FilterRoute()
        : base(
            "realty/filter/{*pathInfo}", 
            new RouteValueDictionary(new 
            { 
                controller = "realty", action = "filter" 
            }), 
            new MvcRouteHandler()
        )
    {
    }

    public override RouteData GetRouteData(HttpContextBase httpContext)
    {
        var rd = base.GetRouteData(httpContext);
        if (rd == null)
        {
            return null;
        }

        var filters = rd.Values["pathInfo"] as string;
        if (string.IsNullOrEmpty(filters))
        {
            return rd;
        }

        var tokens = filters.Split('/');
        if (tokens.Length % 2 != 0)
        {
            throw new Exception("Invalid filter format");
        }

        var index = 0;
        for (int i = 0; i < tokens.Length - 1; i += 2)
        {
            var key = tokens[i];
            var value = tokens[i + 1];
            rd.Values[string.Format("filters[{0}].key", index)] = key;
            rd.Values[string.Format("filters[{0}].value", index)] = value;
            index++;
        }

        return rd;
    }
}

which will be registered in your RegisterRoutes method:

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

    routes.Add("Filter", new FilterRoute());

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