MVC unobtrusive validation on checkbox not working

Question

I'm trying to implement the code as mentioned in this post. In other words I'm trying to implement unobtrusive validation on a terms and conditions checkbox. If the user hasn't selected the checkbox, then the input should be marked as invalid.

This is the server side Validator code, I've added:

/// <summary>
/// Validation attribute that demands that a boolean value must be true.
/// </summary>
[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
public class MustBeTrueAttribute : ValidationAttribute
{
    public override bool IsValid(object value)
    {
        return value != null && value is bool && (bool)value;
    }
}

This is the model

[MustBeTrue(ErrorMessage = "You must accept the terms and conditions")]
[DisplayName("Accept terms and conditions")]
public bool AcceptsTerms { get; set; }

This is my view:

@Html.EditorFor(x => x.AcceptTermsAndConditions)
@Html.LabelFor(x => x.AcceptTermsAndConditions)
@Html.ValidationMessageFor(x => x.AcceptTermsAndConditions)

and this is the jQuery I've used to attach the validator client side:

$.validator.unobtrusive.adapters.addBool("mustbetrue", "required");

The client side script doesn't appear to be kicking in, however. Whenever I press the submit button, validation on the other fields kicks in fine, but the validation for the Terms & conditions doesn't seem to kick in. This is how the code looks in Firebug after I've clicked the submit button.

<input type="checkbox" value="true" name="AcceptTermsAndConditions" id="AcceptTermsAndConditions" data-val-required="The I confirm that I am authorised to join this website and I accept the terms and conditions field is required." data-val="true" class="check-box">
<input type="hidden" value="false" name="AcceptTermsAndConditions">
<label for="AcceptTermsAndConditions">I confirm that I am authorised to join this website and I accept the terms and conditions</label>
<span data-valmsg-replace="true" data-valmsg-for="AcceptTermsAndConditions" class="field-validation-valid"></span>

Any ideas? Have I missed out a step? This is driving me potty!

Thanks in advance S

Answer 1

You need to implement IClientValidatable on your custom attribute in order to tie the mustbetrue adapter name that you are registering on the client side with this attribute:

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
public class MustBeTrueAttribute : ValidationAttribute, IClientValidatable
{
    public override bool IsValid(object value)
    {
        return value != null && value is bool && (bool)value;
    }

    public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context)
    {
        yield return new ModelClientValidationRule
        {
            ErrorMessage = this.ErrorMessage,
            ValidationType = "mustbetrue"
        };
    }
}

---

UPDATE:

Full working example.

Model:

public class MyViewModel
{
    [MustBeTrue(ErrorMessage = "You must accept the terms and conditions")]
    [DisplayName("Accept terms and conditions")]
    public bool AcceptsTerms { get; set; }
}

Controller:

public class HomeController : Controller
{
    public ActionResult Index()
    {
        var model = new MyViewModel();
        return View(model);
    }

    [HttpPost]
    public ActionResult Index(MyViewModel model)
    {
        return View(model);
    }
}

View:

@model MyViewModel

<script src="@Url.Content("~/Scripts/jquery.validate.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.js")" type="text/javascript"></script>
<script type="text/javascript">
    $.validator.unobtrusive.adapters.addBool("mustbetrue", "required");
</script>

@using (Html.BeginForm())
{
    @Html.CheckBoxFor(x => x.AcceptsTerms)
    @Html.LabelFor(x => x.AcceptsTerms)
    @Html.ValidationMessageFor(x => x.AcceptsTerms)
    <input type="submit" value="OK" />
}