How do I process drop down list change event asynchronously? - ajax

Question

I have a drop down list that I need to react to asynchronously. I cannot get the Ajax.BeginForm to actually do an asynchronous postback, it only does a full postback.
using (Ajax.BeginForm("EditStatus", new AjaxOptions { UpdateTargetId = "divSuccess"}))
{%>
<%=Html.DropDownList(
"ddlStatus",
Model.PartStatusList.OrderBy(wc => wc.SortOrder).Select(
wc => new SelectListItem
{
Text = wc.StatusDescription,
Value = wc.PartStatusId.ToString(),
Selected = wc.PartStatusId == Model.PartStatusId
}),
new { #class = "input-box", onchange = "this.form.submit();" }
)%>
<div id='divSuccess'></div>
<%
}
When the user selects an item from the list, it does a full postback and the controller method's return value is the only output on the screen. I am expecting the controller method's return value to be displayed in "divSuccess".
[AjaxAwareAuthorize(Roles = "Supplier_Administrator, Supplier_User")]
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult EditStatus(PartPropertiesViewModel partPropertiesViewModel)
{
var part = _repository.GetPart(partPropertiesViewModel.PartId);
part.PartStatusId = Convert.ToInt32(Request.Form["ddlStatus"]);
_repository.SavePart(part);
return Content("Successfully Updated Status.");
}

Answer 1

How about doing this the proper way using jQuery unobtrusively and getting rid of those Ajax.* helpers?
The first step is to use real view models and avoid the tag soup in your views. Views should not order data or whatever. It's not their responsibility. Views are there to display data that is being sent to them under the form of a view model from the controller. When I see this OrderBy in your view it's just making me sick. So define a clean view model and do the ordering in your controller so that in your view you simply have:
<% using (Html.BeginForm("EditStatus", "SomeControllerName", FormMethod.Post, new { id = "myForm" }) { %>
<%= Html.DropDownListFor(
x => x.Status,
Model.OrderedStatuses,
new {
#class = "input-box",
id = "myDDL"
}
) %>
<% } %>
<div id="divSuccess"></div>
and finally in a completely separate javascript file subscribe for the change event od this DDL and update the div:
$(function() {
$('#myDDL').change(function() {
var url = $('#myForm').attr('action');
var status = $(this).val();
$.post(url, { ddlStatus: status }, function(result) {
$('#divSuccess').html(result);
});
});
});
This assumes that in your controller action you would read the current status like this:
[AjaxAwareAuthorize(Roles = "Supplier_Administrator, Supplier_User")]
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult EditStatus(PartPropertiesViewModel partPropertiesViewModel, string ddlStatus)
{
var part = _repository.GetPart(partPropertiesViewModel.PartId);
part.PartStatusId = Convert.ToInt32(ddlStatus);
_repository.SavePart(part);
return Content("Successfully Updated Status.");
}
And when you see this you might ask yourself whether you really need a form in this case and what's its purpose where you could simply have a dropdownlist:
<%= Html.DropDownListFor(
x => x.Status,
Model.OrderedStatuses,
new Dictionary<string, object> {
{ "class", "input-box" },
{ "data-url", Url.Action("EditStatus", "SomeControllerName") },
{ "id", "myDDL" }
}
) %>
<div id="divSuccess"></div>
and then simply:
$(function() {
$('#myDDL').change(function() {
var url = $(this).data('url');
var status = $(this).val();
$.post(url, { ddlStatus: status }, function(result) {
$('#divSuccess').html(result);
});
});
});