Question

I’m using ASP.NET MVC3 with Razor.

I have a boolean value in my model which I would like to render as a check box in my view. However, I would like the check box to indicate the reverse of the boolean state. In other words, selecting the check box should set the bound model object to false, not true, when the form is submitted. And vice versa.

I can do this to set the value attribute on the rendered check box input element:

@Html.CheckBoxFor(model => model.MyBoolean, new { value = "false" })

But the hidden input element that is automatically created still has a value of false. Thus they both have a value of false, which means the bound model object is always set to false.

So how can I force the HTML helper to set the hidden element to true and the check box element to false?

I know that (a) I could alter the model and the database, (b) I could alter the values with javascript just prior to submission, and (c) I could swap whatever value is received in the controller after submission. I may do one of these, but I’m not asking for possible solutions; I’m asking whether it is possible to make the HTML helper do as I wish. I have searched extensively and haven’t seen this addressed anywhere in official or unofficial sources. It seems like they should have a “swap” option or something.

Answer 1

    class ViewModel {
        public bool MyBoolean {get;set;}
        public bool DisplayValue {
            get {
                return ! MyBoolean ;
            }

            set {
                MyBoolean = !value;
            }
        }
    }

And bind to the DisplayValue as it’s setter updates you MyBoolean property anyway.

EDIT:

After reading your question again:.

You could use HtmlHelper to do that – but instead of using a CheckBox you could use a dropdown. The dropdown will define the “oppisite” values and text.

    myModelInstance.PossibleValues = new[] { new SelectListItem { Value = "false", Text = "Not false" }, new SelectListItem { Value = "true", Text = "Not true" } };

Notice how the description is the opposite meaning of what you want the model to be. So for eg. for true you may have text as “Hidden” and false you may have the text as “Visible”, true for “Disabled” and false for “Enabled” etc.

Then in your View:

    @Html.DropDownList(Model.MyBoolean.ToString(), Model.PossibleValues)

The model will be updated with the correct value without have to do boolean toggles before viewing or updating.