Posting JSON Arrays to a MVC Controller using JQuery 1.4.1

Following up on my April 13^th post, I have the drag and drop working between the 2 tables.  I now want to post the data back to the server for processing

Posting to a server method like so:

        [AcceptVerbs(HttpVerbs.Post)]

        public ActionResult Index(string regionId)

        {

            //Do Something Useful Here

            return View();

        }

(I know that the return will be JSON, not an ActionResult, but one thing at a time)

I set up a simple AJAX call in JQuery like so:

$.post("Region/Index",{regionId: "Hello"});

Things worked great:

I then tried to change the parameter from a single string to an array of strings

        [AcceptVerbs(HttpVerbs.Post)]

        public ActionResult Index(List<String> regionIds)

        {

            //Do Something Useful Here

            return View();

        }

And I changed the AJAX call to this:

            var regionArray = new Array();

            $("#destinationTable tr:gt(0)").each(function () {

                var regionId = $(this).find("#regionId").html();

                regionArray.push(regionId);

            });

            var postData = { regionIds: regionArray };

            $.post("Region/Index", postData);

When looking at Fiddler, data is crossing over the wire:

With the web form view like so:

But the MVC function was not recognizing the input – the paramters were null.  After many hours of searching and trial-by-error, I found this post

Once I changed the $post to $.ajax and specified the traditional attribute, the parameters were filled fine.

Note that

jQuery.ajaxSetting.traditional = true; 

does not work – traditional is not a property of ajaxSetting