CheckBox lists in ASP.NET MVC and bind it back to controller

Question

 Html.CheckBox("SelectedStudents", false, new { @class = "check-item", id = x.Id, value = x.Id })

which produce

<input checked="checked" class="check-item" id="4507" name="SelectedStudents" value="4507" type="checkbox">

<input checked="checked" class="check-item" id="4507" name="SelectedStudents" value="4508" type="checkbox">

<input checked="checked" class="check-item" id="4507" name="SelectedStudents" value="4509" type="checkbox">

In mvc model I have

public IEnumerable<string> SelectedStudents { get; set; }

but when I post back, SelectedStudents are always null. Why? In this howto http://benfoster.io/blog/checkbox-lists-in-aspnet-mvc is written:

The ASP.NET MVC modelbinder is smart enough to map the selected items to this property.

but in my example is always null. Why? How to write more checkboxes and bind it back

Because the blog you posted is using a strongly typed Editor (strongly typed editors end in For like CheckListBoxFor) and you changed it to use a dumb editor (Checkbox). Dumb editors can be model bound back as long as you know exactly what you are doing. — Erik Philips
– Erik Philips, Commented Dec 28, 2015 at 17:17

Moe · Accepted Answer · 2015-12-29 17:06:19Z

You should be using a strongly typed editor to be able to pass the result to the controller (Model binder).

I prefer to do it this way.

Model

public class YourViewModel
{
     public List<SelectListItem> Students
        {
            get;
            set;
        }
}

Controller Get

Students= service.GetStudents(); //Fill the list

View

  @for (var i = 0; i < Model.Students.Count; i++)
                {

                    @Html.CheckBoxFor(m => m.Students[i].Selected)
                    @Html.HiddenFor(m => m.Students[i].Text)
                    @Html.HiddenFor(m => m.Students[i].Value)
                    <span>@Model.Students[i].Text</span>
                }

Controller Post

[HttpPost]
        public ActionResult Create(YourViewModel model)
        {
          foreach(var student in model.Students)
          {
            if(student.Selected) { // Do your logic}
          }
        }

Alternatively You could use an array or List of string. A ListBox is used in this example.

public string[] SelectedStudents{ get; set; }

@Html.ListBoxFor(s => s.SelectedStudents, new MultiSelectList(Model.Students, "Value", "Text", Model.SelectedStudents), new { @class = "form-control", style = "height:250px; width:100%" })

Community · Accepted Answer · 2017-05-23 12:08:20Z

1

See my answer here How to bind checkbox values to a list of ints?.

The nice thing about this is that it separates concerns between your controller and ui nicely. The html extension methods also create correct html using label and input for the checkbox. and there is no need for hidden fields.

edited May 23, 2017 at 12:08

CommunityBot

11 silver badge

answered Dec 28, 2015 at 18:26

Fran

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Comments

J4ime · Accepted Answer · 2015-12-28 15:10:28Z

0

Do you try it with CheckBoxListFor?? You need to associate the checkbox with model and should not have the same ID and name

@Html.CheckBoxListFor(model => model.SelectedSources, Model.SubscriptionSources)

answered Dec 28, 2015 at 15:10

J4ime

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Comments

Chris Pratt · Accepted Answer · 2015-12-28 16:46:27Z

0

You need to use a mutable type, like List<string>.

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

answered Dec 28, 2015 at 16:46

Chris Pratt

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