CA2227 and ASP.NET Model Binding

Question

Lately, I've been working on enabling more of the Visual Studio code analysis rules in my projects. However, I keep bumping into rule CA2227: "Collection properties should be read only".

Say I have a model class like this:

public class Foo
{
    public string Name { get; set; }

    public List<string> Values { get; set; }
}

And I have a strongly-mapped view page:

@using (Html.BeginForm())
{
    @Html.LabelFor(m => m.Name)
    @Html.EditorFor(m => m.Name)
    for (int i = 0; i < Model.Values.Count; i++)
    {
        <br />
        @Html.LabelFor(m => Model.Values[i]);
        @Html.EditorFor(m => Model.Values[i]);
    }

    <button type="submit">Submit</button>
}

With ASP.NET MVC, I can write an action in my controller that will automatically bind this input to a class of type Foo:

[HttpPost]
public ActionResult ProcessForm(Foo model)
{
    return View(model);
}

The problem with this approach, is that my List<string> auto property violates rule CA2227. If I wasn't doing model binding, I could make the property read only and populate the collection elsewhere. However, that approach won't work with the default model binder. For now I've just been adding a suppression message when it occurs in a view model.

Is there a way I can bind a collection of items in a model without violating CA2227? Or is adding a suppression message my best option here?

Have you tried initializing the List before sending it to your View? — Moe Bataineh, Aug 30 '13 at 17:25

score 5 · Accepted Answer · answered Aug 30 '13 at 17:49

5

I believe you would need to create a custom ModelBinder to work around this, which isn't worth it. In this case since there's reasonable benefit to break the rule go ahead and suppress it.

answered Aug 30 '13 at 17:49

STW

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score 1 · Answer 2 · edited Jun 20 '20 at 09:12

This is one one the cases that this rule should be suppressed as these model classes also perform work as transfer data object.

quoting the rule documentation:

When to suppress warnings

You can suppress the warning if the property is part of a Data Transfer Object (DTO) class.
Otherwise, do not suppress warnings from this rule.

https://learn.microsoft.com/pt-br/visualstudio/code-quality/ca2227?view=vs-2019

CA2227 and ASP.NET Model Binding

2 Answers2