How to handle checkboxes in ASP.NET MVC forms?

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This seems a bit bizarre to me, but as far as I can tell, this is how you do it.

I have a collection of objects, and I want users to select one or more of them. This says to me "form with checkboxes." My objects don't have any concept of "selected" (they're rudimentary POCO's formed by deserializing a wcf call). So, I do the following:

public class SampleObject{
  public Guid Id {get;set;}
  public string Name {get;set;}
}

In the view:

<%
    using (Html.BeginForm())
    {
%>
  <%foreach (var o in ViewData.Model) {%>
    <%=Html.CheckBox(o.Id)%>&nbsp;<%= o.Name %>
  <%}%>
  <input type="submit" value="Submit" />
<%}%>

And, in the controller, this is the only way I can see to figure out what objects the user checked:

public ActionResult ThisLooksWeird(FormCollection result)
{
  var winnars = from x in result.AllKeys
          where result[x] != "false"
          select x;
  // yadda
}

Its freaky in the first place, and secondly, for those items the user checked, the FormCollection lists its value as "true false" rather than just true.

Obviously, I'm missing something. I think this is built with the idea in mind that the objects in the collection that are acted upon within the html form are updated using UpdateModel() or through a ModelBinder.

But my objects aren't set up for this; does that mean that this is the only way? Is there another way to do it?

Answer 1

HtmlHelper adds an hidden input to notify the controller about Unchecked status. So to have the correct checked status:

bool bChecked = form[key].Contains("true");

Answer 2

This issue is happening in the release 1.0 as well. Html.Checkbox() causes another hidden field to be added with the same name/id as of your original checkbox. And as I was trying loading up a checkbox array using document.GetElemtentsByName(), you can guess how things were getting messed up. It's a bizarre.

Answer 3

Here's what I've been doing.

View:

<input type="checkbox" name="applyChanges" />

Controller:

var checkBox = Request.Form["applyChanges"];

if (checkBox == "on")
{
...
}

I found the Html.* helper methods not so useful in some cases, and that I was better off doing it in plain old HTML. This being one of them, the other one that comes to mind is radio buttons.

Edit: this is on Preview 5, obviously YMMV between versions.

Answer 4

@Dylan Beattie Great Find!!! I Thank you much. To expand even further, this technique also works perfect with the View Model approach. MVC is so cool, it's smart enough to bind an array of Guids to a property by the same name of the Model object bound to the View. Example:

ViewModel:

public class SampleViewModel
{
    public IList<SampleObject> SampleObjectList { get; set; }
    public Guid[] SelectedObjectIds { get; set; }

    public class SampleObject
    {
        public Guid Id { get; set; }
        public string Name { get; set; }
    }
}

View:

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
<h2>Sample View</h2>
<table>
    <thead> 
        <tr>
            <th>Checked</th>
            <th>Object Name</th>
        </tr>
    </thead> 
<% using (Html.BeginForm()) %>
<%{%>                    
    <tbody>
        <% foreach (var item in Model.SampleObjectList)
           { %>
            <tr>
                <td><input type="checkbox" name="SelectedObjectIds" value="<%= item.Id%>" /></td>
                <td><%= Html.Encode(item.Name)%></td>
            </tr>
        <% } %>
    </tbody>
</table>
<input type="submit" value="Submit" />
<%}%>                    

Controller:

    [AcceptVerbs(HttpVerbs.Get)]
    public ActionResult SampleView(Guid id)
    {
        //Object to pass any input objects to the View Model Builder 
        BuilderIO viewModelBuilderInput = new BuilderIO();

        //The View Model Builder is a conglomerate of repositories and methods used to Construct a View Model out of Business Objects
        SampleViewModel viewModel = sampleViewModelBuilder.Build(viewModelBuilderInput);

        return View("SampleView", viewModel);
    }

    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult SampleView(SampleViewModel viewModel)
    {
        // The array of Guids successfully bound to the SelectedObjectIds property of the View Model!
        return View();
    }

Anyone familiar with the View Model philosophy will rejoice, this works like a Champ!

Answer 5

How about something like this?

bool isChecked = false;
if (Boolean.TryParse(Request.Form.GetValues(”chkHuman”)[0], out isChecked) == false)
    ModelState.AddModelError(”chkHuman”, “Nice try.”);

Answer 6

I had nearly the same Problem but the return Value of my Controller was blocked with other Values.

Found a simple Solution but it seems a bit rough.

Try to type Viewbag. in your Controller and now you give it a name like Viewbag.Checkbool

Now switch to the View and try this @Viewbag.Checkbool with this you will get the value out of the Controller.

My Controller Parameters look like this:

public ActionResult Anzeigen(int productid = 90, bool islive = true)

and my Checkbox will update like this:

<input id="isLive" type="checkbox" checked="@ViewBag.Value" ONCLICK="window.location.href = '/MixCategory/Anzeigen?isLive=' + isLive.checked.toString()" />