MVC 5通用列表绑定到局部视图

Question

I'm having an issue with the bindings of my model to a partial view and feel that there must be a way to do what I want. I wonder if my design is flawed and a small refactoring might be necessary.

A very simplified (and abstract) version of my models would be like so:

Public Class BaseClass
{
    Public string Name { get; set; }
    Public List<SomeClass> Things { get; set; }
}

Public Class DerivedClass : BaseClass
{
    Public List<LineItem> Items { get; set; }
}

Public Class Library
{
    Public List<LineItem> Items { get; set; }
}

Public Class LineItem
{
    Public string Name { get; set; }
    Public string Value { get; set; }
}

I have Editor Templates for the BaseClass, SomeClass, and LineItem. These are shown in the view for DerivedClass and work as intended by submitting changes to the controller. The LineItem template is wrapped in a LineItemList partial view because I intend to use it for a view for Library and don't want to repeat all of that layout and javascript. The LineItemList partial view is included on the DerivedClass view by Html.PartialView since there doesn't seem to be a way to create an Editor Template for the List type. So my views look like this:

• DerivedClassView
  • BaseClassPartialView
    • SomeClassPartialView
  • LineItemListPartialView
    • LineItemParialView

When I submit my form, the controller gets all of the data for the BaseClass and SomeClass list but none for the LineItem list. The difference of course being that one is rendered using Html.EditorFor and the other Html.PartialView.

Refactoring the classes will be tough as they have to be backwards compatible with an old XML format for serialization, but I'm sure I can work some magic if necessary.

As Chris Pratt mentioned, I forgot to include my controller methods:

Public ActionResult DerivedClassEditor()
{
    Return View(New DerivedClass());
}

[HttpPost]
Public ActionResult DerivedClassEditor(DerivedClass dc)
{
    // Do Stuff
}

I just noticed in the rendered Html, the SomeClass controls are named SomeClass.[0].Name while those of the LineItem are [0].Name . I have a feeling that might be a symptom of the issue.

And my views look similar to this:

DerivedClassEditor

@model DerivedClass

@using (Html.BeginForm())
{
    @Html.EditorFor(model => model)

    @Html.Partial("LineItemListPartialView")

    <input type="submit" />
}

LineItemListPartialView

@model List<LineItem>

<div name="Items">
    @Html.EditorFor(model => model)
</div>

LineItemPartialView

@model LineItem

<div name="LineItem">
    @Html.LabelFor(model => model.Name)
    @Html.TextEditorFor(model => model.Name)
</div>

Edit :

A link to my view: https://github.com/melance/TheRandomizer/blob/Initial/TheRandomizer.WebApp/Views/UserContent/AssignmentEditor.cshtml

I've narrowed down the issue to the fact that when I load one of the lists using @Html.EditorFor it names the inputs Collection[index].Property yet when I add one dynamically using the same call it simply names the input Property . Is there an easy and reusable way to have the addition of new items have the same naming structure?

Answer 1

Crucially, you failed to post your controller code, so I'm stabbing in the dark, but I think I can guess pretty well what's happening. You most likely have something like:

[HttpPost]
public ActionResult MyAwesomeAction(BaseClass model)
{
    ...
}

And you're assuming that since your view is working with DerivedClass and posting DerivedClass that you should end up with an instance of DerivedClass rather than BaseClass in your action. That assumption is incorrect.

All that exists on post is a set of string key-value pairs. The modelbinder looks at the action signature and attempts to bind the posted data to an instance of the parameter(s), newing up classes as necessary. Given this, the only information the modelbinder has in this scenario is that it's expected to bind values to an instance of BaseClass and a set of data to attempt to do that with. As a result, it will create an instance of BaseClass and bind what data it can, dropping anything it can't. Importantly, since BaseClass doesn't include stuff like your Items property, all of that data will be discarded.

Long and short, polymorphism isn't supported with action parameters. The type of your parameter must be the type you want. Period.

For what it's worth, you can use editor templates for list properties. EditorFor will simply render the editor template for the contained type for each item in the list. For example, calling:

@Html.EditorFor(m => m.Items)

Is essentially the same as:

@for (var i = 0; i < Model.Items.Count(); i++)
{
    @Html.EditorFor(m => m.Items[i])
}

Answer 2

So after much research, trial and error and help from Erik, I was able to solve my problem. The issue turned out to be the naming of the form elements in my partial view. When added by the model they are indexed as such: name = "ListProperty[Index].PropertyName" . When I was adding my partial views using ajax, the were named for just the Property Name. In order to fix this, I had to handle my ajax calls for the partial view like this:

public ActionResult CreateParameter(Int32 index)
{
    ViewData.TemplateInfo.HtmlFieldPrefix = $"Parameters[{index}]";
    return PartialView("~/Views/Shared/EditorTemplates/Configuration.cshtml");
}