MVC Ajax not posting a dropdownlist value - asp.net

Question

Using the following form in a view
<% using (Ajax.BeginForm("PatientSearch", new {}, new AjaxOptions()
{
HttpMethod = "POST",
UpdateTargetId = "searchResults",
OnBegin = "BeginRequest",
OnSuccess = "SuccessRequest",
OnFailure = "FailRequest"
}))
{ %>
<%=Html.DropDownList("patientType",(SelectList)ViewData["PatientTypeList"]) %>
<%=Html.DropDownList("edCenterID",(SelectList)ViewData["EdCenterList"]) %><br />
<input type="submit">
<%} %>
Results in the following HTML
<select id="patientType" name="patientType">
<option selected="selected">Referral</option>
<option>Patient</option>
</select>
<select id="edCenterID" name="edCenterID">
<option value="2">Barren River District Health Department</option>
<option value="3">Madison County Health Department</option>
</select>
and I attempt to catch the values with the code in the my controller
public ActionResult PatientSearch(string patientType, int edCenterID) {
//do something with values
}
patientType is always passed as ""; however, edCenterID is posted and received just fine.
If I change this from an Ajax.BeginForm to an HTML.BeginForm, everything works perfectly.
Is the problem in my DropDownList, my controller, both?
ADDED FROM COMMENTS
#Eoin pointed out to me that my select is rendering without a value and that is probably the problem. That brings up two questions:
1. Why does it work with the a standard post, but not an Ajax post.
2. How do I get my dropdownlist to contain a value with the list is a simple string only list (no key). I am posting the code used to generate my SelectList below
ViewData["PatientTypeList"]=new SelectList(new List<string>()
{ "Referral", "Patient"});

Answer 1

Does the patientType List have a .Value
By the looks of things, theres no value being rendered for the PatientType DDL <option>'s so essentially every option has a value="" so it is actually post back the correct value.
The problem is with what's being rendered in the first place.
edit
Try
Dictionary<string, string> d = new Dictionary<string, string>();
d.Add("referral", "referral");
d.Add("patient", "patient");
ViewData["PatientTypeList"]=new SelectList(d, "Key", "Value");

Answer 2

Is there no solution to this? Seems like something is broken in the Ajax form submission.
Here is a good fix, write your methods as normal, then run:
function addDropDownValues() {
$("select option").each(function(i) {
if ($(this).text() == "Red") { $(this).attr('value', "Red"); }
else if ($(this).text() == "Amber") { $(this).attr('value', "Amber"); }
else if ($(this).text() == "Green") { $(this).attr('value', "Green"); }
else if ($(this).text() == "Complete") { $(this).attr('value', "Complete"); }
});
}
Where "red", "amber", etc... are the values you want to be passed through
This will append a value to each dropdown, producing:
<select name="status1" id="status1"><option value="Red">Red</option>
<option value="Amber">Amber</option>
<option selected="selected" value="Green">Green</option>
<option value="Complete">Complete</option>
</select>
This will work with both Firefox AND Internet Explorer. Internet Explorer requires the value item, firefox does not.