ASP.NET - Why is my cookie not persisted? - asp.net-mvc

Question

i'm trying to set a cookie to store a selected department in. The cookie is set with a small form which has a select-dropdown with departments. This is posted using AJAX.
This is how I store the cookie:
<AcceptVerbs(HttpVerbs.Post)> _
Function ChangeDepartment(ByVal FormValues As FormCollection) As ActionResult
If Response.Cookies("department") IsNot Nothing Then
Response.Cookies("department").Value = FormValues("department")
Else
Dim c As New HttpCookie("department")
c.Value = FormValues("department")
c.Expires = Now.AddDays(7)
Response.Cookies.Add(c)
End If
Return Json(New With {.newDepartment = Response.Cookies("department").Value})
End Function
The .newDepartment variable is returned correctly with the correct value.
This is how I retrieve the cookie and build the select-dropdown:
<% Ajax.BeginRouteForm("ChangeDepartment", New AjaxOptions With {.LoadingElementId = "loading", .HttpMethod = "post", .OnSuccess = "function(request) {ajaxMessage('Department change', 'Department changed to: ' + request.get_response().get_object().newDepartment);}"})%>
<select name="department">
<option>Default</option>
<option<%If Request.Cookies("department") Isnot Nothing andAlso Request.Cookies("department").Value = "Supervisor" Then Response.Write (" selected=""selected""") %>>Supervisor</option>
<option<%If Request.Cookies("department") Isnot Nothing andAlso Request.Cookies("department").Value = "Purchasing" Then Response.Write (" selected=""selected""") %>>Purchasing</option>
<option<%If Request.Cookies("department") Isnot Nothing andAlso Request.Cookies("department").Value = "Engineering" Then Response.Write (" selected=""selected""") %>>Engineering</option>
</select>
<input type="submit" value="Change department" />
<% Html.EndForm%>
The cookie isn't stored, because the select-dropdown keeps going back to Default. Am I doing something wrong?

Answer 1

You could try to use http debugger like Fiddler for IE and HttpFox for FireFox.
Check if the cookie is really send with the server response and if the browser sends it back with further requests.
From there you are probably going to track the problem and see what is going wrong. If you still have problems you could post the http traffic here.