New value in HTML.DropDownListFor(...) not setting in Controller [Post] method? - asp.net-mvc

Question

Hopefully someone can see how to go about this, because I've tried everything I can think of. When the Create() View in my MVC5 application loads I first populate several [SelectList(...)]'s in my Controller (ex.):
ViewBag.Model_Id = new SelectList(db.DBT_MODELS.OrderBy(x => x.MODEL_DESCRIPTION), "MODEL_ID", "MODEL_DESCRIPTION");
I then on my Create() View use this [SelectList(...)] to Populate an Html.DropDownListFor(...):
<div class="form-group">
<span class="control-label col-md-2">Model:</span>
<div class="col-md-4">
#Html.DropDownListFor(model => model.MODEL_ID, (SelectList)ViewBag.Model_Id, htmlAttributes: new { #class = "form-control dropdown", #id = "selectModel" })
#Html.ValidationMessageFor(model => model.MODEL_ID, "", new { #class = "text-danger" })
</div>
<div class="col-md-2">
<div class="btn-group">
<button id="createNewModel" type="button" class="btn btn-success" aria-expanded="false">CREATE NEW</button>
</div>
</div>
<div class="col-md-4">
<div id="createModelFormContainer" style="display:none">
<form action="/createNewModel">
<input type="text" id="textNewModel" name="model_description" placeholder="New Model" />
<input type="button" id="submitNewModel" value="Submit" />
<input type="button" id="cancelNewModel" value="Cancel" />
</form>
</div>
</div>
</div>
Simple enough, and this all works as expected. The problem lies in a bit of extended functionality I've tried to incorporate. My main class has several of these properties which are basically Foreign Key's in my DB. When a User goes in to Create/Edit() an entity in my main Model, I wanted to allow them to be able to add new entities to these foreign tables without needing to navigate away from the current View.
As such, I added (for each foreign property, using (Model) as an example) the code shown above and again directly below with a button to Show/Hide a small form for users to insert a new value and have it added to the DropDownList:
<div class="col-md-2">
<div class="btn-group">
<button id="createNewModel" type="button" class="btn btn-success" aria-expanded="false">CREATE NEW</button>
</div>
</div>
<div class="col-md-4">
<div id="createModelFormContainer" style="display:none">
<form action="/createNewModel">
<input type="text" id="textNewModel" name="model_description" placeholder="New Model" />
<input type="button" id="submitNewModel" value="Submit" />
<input type="button" id="cancelNewModel" value="Cancel" />
</form>
</div>
</div>
My submitNewModel() click event below gets the user's inputted new value and then uses a JSON call to a Controller Method to add it in the Database Table. This new value (and new ID for it) are then returned, the form for the DropDownList is reset, and I set the DropDownList's current value as the newly added one:
$('#createNewModel').click(function () {
$('#createModelFormContainer').show();
})
$('#cancelNewModel').click(function () {
$('#createModelFormContainer').hide();
})
$('#submitNewModel').click(function () {
var form = $(this).closest('form');
var data = { description: document.getElementById('textNewModel').value };
$.ajax({
type: "POST",
dataType: "JSON",
url: '#Url.Action("createNewModel", "INV_ASSETS")',
data: data,
success: function (resp) {
if (resp.ModelExists)
{
alert("Model [" + resp.Text + "] already exists. Please select from the DropDown.");
} else {
$('#selectModel').append($('<option></option>').val(resp.MODEL_ID).text(resp.Text));
form[0].reset();
$('#createModelFormContainer').hide();
var count = $('#selectModel option').size();
$('#selectModel').prop('selectedIndex', count - 1);
$('#selectModel').val(resp.MODEL_ID);
//document.getElementById('selectModel').value = resp.MODEL_ID; - Shows dropdown as blank [ ] once executed.
}
},
error: function () {
alert("ERROR - Something went wrong adding new Model [" + resp.Text + "]!");
$('#createModelFormContainer').hide();
}
});
//reloadForNewEntity();
});
The createNewModel() method that is called in my Controller:
public JsonResult createNewModel(string description)
{
DBT_MODELS model = new DBT_MODELS()
{
// ID auto-set during save.
MODEL_DESCRIPTION = description.Trim(),
CREATED_DATE = DateTime.Now,
CREATED_BY = System.Environment.UserName
};
var duplicateModel = db.DBT_MODELS.FirstOrDefault(x => x.MODEL_DESCRIPTION.ToUpper() == model.MODEL_DESCRIPTION.ToUpper());
try
{
if (duplicateModel == null)
{
if (ModelState.IsValid)
{
db.DBT_MODELS.Add(model);
db.SaveChanges();
// Ensure the [model.ID] is properly set after having been saved to and auto-generated in the database.
model.MODEL_ID = db.DBT_MODELS.FirstOrDefault(x => x.MODEL_DESCRIPTION.ToUpper() == model.MODEL_DESCRIPTION.ToUpper()).MODEL_ID;
}
}
else
{
model = duplicateModel;
}
}
catch (Exception ex)
{
Elmah.ErrorSignal.FromCurrentContext().Raise(ex);
}
return Json(new { ID = model.MODEL_ID, Text = model.MODEL_DESCRIPTION, ModelExists = (duplicateModel != null) }, JsonRequestBehavior.AllowGet);
}
Visually speaking, everything works as intended up to this point. The problem is when I go to Save the main entity I am Creating/Editing.
Any value that was already in the Foreign Tables, and thus in the DropDownList when the View loads, saves just fine; but if I add a new Foreign Table value for these main entity properties (though visually added and the currently selected values for the individual DropDownLists) the [POST] method then executes with each foreign id value set as 0 (ex. MainClass.Model_ID = "0" vs expected MainClass.Model_ID = "625", MainClass.Type_ID = "0" vs expected MainClass.Type_ID = "17", MainClass.Location_ID = "0" vs expected MainClass.Location_ID = "82", etc.)
Basically if the value selected in the Html.DropDownListFor() is one of my newly added values, the POST controller method always renders the MainClass.*_ID value which the selected Html.DropDownListFor() value corresponds to as "0".
Can anyone point me to how to get this working? I have tried:
Changing how my JavaScript sets the value in the DropDownList after the the JSON call to my Controller Actions returns (ex): //document.getElementById('selectModel').value = resp.MODEL_ID; - Shows dropdown as blank [ ] once executed. vs $('#selectModel').val(resp.MODEL_ID); which visually renders the expected new value in the DropDownList.
On return from the Controller method, setting a new ViewBag variable and then hoping to reference the saved value in the POST method (did not work, the JavaScript rendered my #Viewbag.PostModelID = resp.ModelID as "= resp.ModelID" and threw many expected errors).
EDIT:
[Redacted for N/A]
EDIT2: Good to go. Thanks everyone for the suggestions!

Answer 1

The json data you are returning from your action method is in this format.
{
"ID": 24,
"Text": "IOS",
"ModelExists": false
}
But in your code, you are trying to access MODEL_ID property which does not exist in the resp object.
$('#selectModel').append($('<option></option>').val(resp.MODEL_ID).text(resp.Text));
Change your code to use ID property value
$('#selectModel').append($('<option></option>').val(resp.ID).text(resp.Text));
$('#selectModel').val(resp.ID);

Answer 2

In your controller where you create the new model.. your json object that you're returning is ID, Text, ModelExists, but in your javascript you're setting the val property of the new <option> to MODEL_ID.. these 2 need to match..
So change your javascript to be
.val(resp.ID)
or change the return value in your controller action to
return Json(new { MODEL_ID = model.MODEL_ID, Text = model.MODEL_DESCRIPTION
You're also referencing MODEL_ID here
$('#selectModel').val(resp.MODEL_ID);
so make sure if you don't change your controller action, you update this also