ASP.Net MVC RouteData and arrays

Question

If I have an Action like this:

public ActionResult DoStuff(List<string> stuff)
{
   ...
   ViewData["stuff"] = stuff;
   ...
   return View();
}

I can hit it with the following URL:

http://mymvcapp.com/controller/DoStuff?stuff=hello&stuff=world&stuff=foo&stuff=bar

But in my ViewPage, I have this code:

<%= Html.ActionLink("click here", "DoMoreStuff", "MoreStuffController", new { stuff = ViewData["stuff"] }, null) %>

Unfortunately, MVC is not smart enough to recognize that the action takes an array, and unrolls the list to form the proper url route. instead it just does a .ToString() on the object which just lists the data type in the case of a List.

Is there a way to get Html.ActionLink to generate a proper URL when one of the destination Action's parameters is an array or list?

-- edit --

As Josh pointed out below, ViewData["stuff"] is just an object. I tried to simplify the problem but instead caused an unrelated bug! I'm actually using a dedicated ViewPage<T> so I have a tightly coupled type aware Model. The ActionLink actually looks like:

<%= Html.ActionLink("click here", "DoMoreStuff", "MoreStuffController", new { stuff = ViewData.Model.Stuff }, null) %>

Where ViewData.Model.Stuff is typed as a List

Answer 1

I'm thinking that a custom HtmlHelper would be in order.

 public static string ActionLinkWithList( this HtmlHelper helper, string text, string action, string controller, object routeData, object htmlAttributes )
 {
     var urlHelper = new UrlHelper( helper.ViewContext.RequestContext );


     string href = urlHelper.Action( action, controller );

     if (routeData != null)
     {
         RouteValueDictionary rv = new RouteValueDictionary( routeData );
         List<string> parameters = new List<string>();
         foreach (var key in rv.Keys)
         {
             object value = parameters[key];
             if (value is IEnumerable && !(value is string))
             {
                 foreach (string val in (IEnumerable)value)
                 {
                     parameters.Add( string.Format( "{0}={1}", key, val );
                 }
             }
             else
             {
                 parameters.Add( string.Format( "{0}={1}", key, value ) );
             }
         }
         string paramString = string.Join( "&", parameters.ToArray() );
         if (!string.IsNullOrEmpty( paramString ))
         {
            href += "?" + paramString;
         }
     }

     TagBuilder builder = new TagBuilder( "a" );
     builder.Attributes.Add("href",href);
     builder.MergeAttributes( new RouteValueDictionary( htmlAttributes ) );
     builder.SetInnerText( text );
     return builder.ToString( TagRenderMode.Normal );
}

Answer 2

I'm not at my workstation, but how about something like:

<%= Html.ActionLink("click here", "DoMoreStuff", "MoreStuffController", new { stuff = (List<T>)ViewData["stuff"] }, null) %>

or the typed:

<%= Html.ActionLink("click here", "DoMoreStuff", "MoreStuffController", new { stuff = (List<T>)ViewData.Model.Stuff }, null) %>

Answer 3

you can suffix your routevalues with an array index like so:

        RouteValueDictionary rv = new RouteValueDictionary();

        rv.Add("test[0]", val1);
        rv.Add("test[1]", val2);

this will result in the querystring containing test=val1&test=val2

that might help ?