Passing an array to RouteValues and have it render model binder-friendly url

Question

When passing a RouteValueDicitonary or anonymous object into a @Url.Action method (or any of its analogs), is there a way to properly pass in a collection object or IEnumerable so that it would generate a url that would be compatible with the default model binder?

For example, say I have an action like this:

public ActionResult Index(ICollection<int> ids)
  {
    ...do something
  }

and in my template I do something like this:

@Url.Action("Index", routeValues:new int[]{1,2,3})

the goal is to have a url output like this:

... /index?ids=1&ids=2&ids=3

but the url output is actually something like this:

... /index?ids=System.Int[]

I'm assuming there is no support for this currently. If not, then at what part in MVC do I need to create a custom handler or whatever to override this default functionality?

Answer 1

Unfortunately currently there is no existing helper that will allow you to generate such url. So one possibility is to do it manually:

@(Url.Action("Index") + "?" + string.Join("&", new int[] { 1, 2, 3 }.Select(x => "ids=" + x)))

or write an extension method to encapsulate the logic:

@Url.ActionWithIds("Index", new int[] { 1, 2, 3 })

Since those are integers we don't need url encoding but if you want to do the same thing with a collection of strings the values should be properly url encoded.

Answer 2

Pass each element of the array to a RouteValueDictionary using the model binding syntax for round trip purposes.

int i = 0;
var temprvd = arr.ToDictionary(m => String.Format("name[{0}]", i++), m => (object) m);
@Url.Action("index", new RouteValueDictionary(temprvd));

or concat on to an existing route value dictionary.

Cast the value to an object (as shown above) to ensure the correct RouteValueDictionary constructor overload is used.

Answer 3

For use the default model binder, you should end up with something like :

?ids=1&ids=2&ids=3

you can returns a private collection named HttpValueCollection even the documentation says it's a NameValueCollection using the ParseQueryString utility. Then add the keys manually, HttpValueCollection do the encoding for you. And then just append the QueryString manually :

var qs = HttpUtility.ParseQueryString(""); 
new List<int> { 1, 2, 3, 4, 5 }.ForEach(x => qs.Add("ids", x.ToString()));

@Url.Action("Index")?@qs