MVC 4 Model not returned to controller - asp.net-mvc-4

Question

I have three cascading dropdowns using Ajax to populate themselves on a view. Also in the view I call a partial view that iterates a container in the model and for each item calls another partial to display for editing the model properties appropriate according to the selected items in the dropdowns. I have built a complex model that contains the dropdown choices as well as the properties to be edited, and pass the portion of the model to the lowest level partial necessary to display the properties to be edited.
I want to update the db when the user clicks the submit button, through a normal Html.BeginForm, not by using Ajax. So I must wrap only the partials that display the properties in the form so that the existing Ajax functionality does not post to the controller. The problem is that although I can build this all, and the submit button connects to the controller as expected, the model returns to the controller null.
Does the model not come back from the partials up through the path that built them? Or more correctly stated, does the model not persist on the page even if it is built using partials?
I am sure someone is going to suggest that I post back using Ajax but that is not a best option for me. Or someone might ask what the html looks like on the page. Oddly, I can only see the complete html using browser developer tools, it does not show in a View Source selection.
Any ideas?
Moving this to where it belongs:
I'm not certain I understand. I get that the returning model needs to match the expected model but I don't get the explanation above. You say "So if your controller looks like this:", and of course it does, then what? That's wrong?
I have to look in dev tools for Chrome to see the actual html output and I see this in one case:
<input class="text-box single-line" id="status_Comments" name="status.Comments" type="text" value="Last Install to be completed this weekend">
So if the 'name' tag needs to look proper, I think it does. Am I wrong?
My date fields look like this:
<input type="text" value="8/19/2014" class="datepicker hasDatepicker" id="dp1391795955619">
So there's no 'name' tag but does have an id. Do I need to add a name?
Here's the code that generates the above:
#foreach (Status status in Model) {
string date = status.Date.HasValue ? status.Date.Value.ToShortDateString() : string.Empty;
<tr>
<td style="width: 175px;">#Html.DisplayFor(model => status.Name)</td>
<td style="width: 75px;">#Html.DisplayDropdownColorFor(model => status.StatusValue)</td>
<td style="width: 80px;"><input type="text" value="#date" class="datepicker" /></td>
<td style="width: 80px;"><input type="text" value="" class="datepicker" /></td>
<td style="width: 375px;">#Html.EditorFor(model => status.Comments)</td>
</tr>
}`
Geez, I sound like a desperate moron.
Thanks for your help.

Answer 1

Let's say you had a couple of classes like this:
public class SomeClass1
{
public string Name { get; set; }
public SomeClass2 class2Value { get; set; }
}
public class SomeClass2
{
public string Description { get; set; }
}
And you have a form in a Razor view:
#model SomeClass1
#using (Html.BeginForm()) {
<fieldset>
<div class="editor-label">
#Html.LabelFor(model => model.Name)
</div>
<div class="editor-field">
#Html.EditorFor(model => model.Name)
</div>
<div class="editor-label">
#Html.LabelFor(model => model.class2Value.Description)
</div>
<div class="editor-field">
#Html.EditorFor(model => model.class2Value.Description)
</div>
<p>
<input type="submit" value="Save" />
</p>
</fieldset>
}
The actual HTML code is going to look something like this:
<form id="form1" action="/pageurl" method="POST">
<fieldset>
<div class="editor-label">
Name
</div>
<div class="editor-field">
<input type="text" name="Name" id="Name" value="Name val 1" />
</div>
<div class="editor-label">
Description
</div>
<div class="editor-field">
#Html.EditorFor(model => model.class2Value.Description)
<input type="text" name="class2Value.Description" id="class2Value_Description" value="Desc val 2" />
</div>
<p>
<input type="submit" value="Save" />
</p>
</fieldset>
</form>
If you notice, the name attribute of the form fields are set by MVC to follow the model. In the case of the nested object, it uses the underscore in the ID and period in the name to keep track of the where in the post model the values should go.
So if your controller looks like this:
[HttpPost]
protected ActionResult Save(SomeClass1 model)
{
//Then
// SomeClass1.Name == "Name val 1"
// and
// SomeClass1.class2Value.Description == "Desc val 2"
}
That's what #David was getting at in the comments... No matter how complex your page, when the <form> posts back to the server, the name attributes of the fields you are returning have to line up with the model that the controller action is expecting... or you will get null values.
You can even create a custom class for the post model, and as long as the name attributes line up with the model, and even though it was not the same as the #model at the top of the Razor view, MVC will use the key/value pairs and populate the data in your post model.
UPDATE
I updated the above to reflect a correction. The underscore is the delimiter in the ID attribute, and the period is used in the NAME attribute.
#leemid: An HTML form only posts fields with a name attribute. Only the name'ed inputs, selects, textareas, etc. will be passed back to the server when the form is submitted. And those names have to be inline with the model that is expected by the controller. For the sake of sounding redundant, that date input field you showed the example for, does not have a name attibute, and if the name were the same as the id, there would have to be a property in your model like
public string dp1391795955619 { get; set; }
for it to show up in your in controller action. You can set the name manually, as long as it's named the way MVC is expecting so that it can pass it into the model when posting.
In my example, the parts I was trying to highlight was the relationship between the class and property names, versus the name attributes MVC writes to the HTML document, and how it keeps all that stuff straight. In simple examples, you don't have to think about it. But in your complex scenario, it looks like you're going to have to manage some of the naming conventions manually so that MVC can understand what you're trying to do.