How do you link to an action that takes an array as a parameter (RedirectToAction and/or ActionLink)?

Question

I have an action defined like so:

public ActionResult Foo(int[] bar) { ... }

Url's like this will work as expected:

.../Controller/Foo?bar=1&bar=3&bar=5

I have another action that does some work and then redirects to the Foo action above for some computed values of bar.

Is there a simple way of specifying the route values with RedirectToAction or ActionLink so that the url's get generated like the above example?

These don't seem to work:

return RedirectToAction("Foo", new { bar = new[] { 1, 3, 5 } });
return RedirectToAction("Foo", new[] { 1, 3, 5 });

<%= Html.ActionLink("Foo", "Foo", new { bar = new[] { 1, 3, 5 } }) %>
<%= Html.ActionLink("Foo", "Foo", new[] { 1, 3, 5 }) %>

However, for a single item in the array, these do work:

return RedirectToAction("Foo", new { bar = 1 });
<%= Html.ActionLink("Foo", "Foo", new { bar = 1 }) %>

When setting bar to an array, it redirects to the following:

.../Controller/Foo?bar=System.Int32[]

Finally, this is with ASP.NET MVC 2 RC.

Thanks.

Answer 1

There are a few ways to do this. If you want to keep it stateless avoid using TempData and create a action filter.

Somthing like this:

ActionFilter:

public class BindArrayAttribute:ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        var keys = filterContext.HttpContext.Request.QueryString.AllKeys.Where(p => p.StartsWith("id"));

        var idArray = new int[keys.Count()];

        var counter = 0;
        foreach (var key in keys)
        {
            var id = filterContext.HttpContext.Request.QueryString[key];
            idArray[counter] = int.Parse(id);
            counter++;
        }

        filterContext.ActionParameters["id"] = idArray;

        base.OnActionExecuting(filterContext);
    }
}

Controller:

 [HttpPost]
    public ActionResult Index(ItemModel model)
    {
        var dic = new RouteValueDictionary();

        var counter = 0;
        foreach (var id in model.SelectedItemIds)
        {
            dic.Add("id" + counter, id);
            counter++;
        }

        return RedirectToAction("Display", dic);
    }

    [HttpGet]
    [BindArray]
    public ActionResult Display(int[] id = null)
    {
        return View(id);
    }

Answer 2

I'm not sure how to accomplish that using the existing helpers. But you could write your own method to do so.

Here's something I threw together:

    public static string EnumerableActionLink(this HtmlHelper htmlHelper, string linkText, string controllerName, string actionName, IEnumerable enumerable, string variableName)
    {
        var builder = new StringBuilder(string.Format("/{0}/{1}?", controllerName, actionName));

        foreach (var item in enumerable)
            builder.Append(string.Format("{0}={1}&", variableName, item));

        return string.Format("<a href=\"{0}\">{1}</a>", builder, linkText);
    }

Usage example:

<%= Html.EnumerableActionLink("Foo", "Foo", "Foo", new[] { 1, 3, 5 }, "bar")%>