Data Annotations Checkbox

Question

Is there a way to validate bool checkboxes using Data Annotations in C# MVC?

All the examples I have seen for the custom data annotation approach are just validating one checkbox like a Accept Terms box. I need to validate that at least one checkbox has been selected in a List<>

For Example:

public class QuestionOptionViewModel
{
    public int? Id { get; set; }

    public string Text { get; set; }

    public string QuestionType { get; set; }

    [RequiredIf("QuestionType", "text", ErrorMessage = "Required Field")]
    public string Value { get; set; }

    [RequiredIf("QuestionType", "checkbox", ErrorMessage = "Required Field")]
    public bool IsChecked { get; set; }
}

I am storing a list of IsChecked. I wanted to know rather one of the Checkboxes in the list was selected using Data Annotations.

Answer 1

ViewModel

public class VisitorAgreementTermViewModel
{
    [Required]
    [Display(Name = "Message Accept.")]
    //[Range(typeof(bool), "true", "true", ErrorMessage = "Error Message Text.")]
    [RegularExpression("True", ErrorMessage = "Error Message Text.")]
    public bool Agreement { get; set; }
}

View

@using (Ajax.BeginForm("AgreementTerms", "Visitors", new AjaxOptions()
{
    HttpMethod = "POST",
    UpdateTargetId = "document-body",
    InsertionMode = InsertionMode.Replace,
    LoadingElementId = "document-loading",
    OnBegin = "ClearBody('document-body')"
}))
{
    @Html.AntiForgeryToken()

<div class="row">
    <div class="form-group m-b-xl col-md-offset-1">
        <label class="checkbox-inline">
            @Html.CheckBoxFor(model => model.Agreement)
            @Html.LabelFor(model => model.Agreement)
            <br />
            @Html.ValidationMessageFor(model => model.Agreement, "", new { @class = "text-danger" })
            @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        </label>
    </div>
    <div class="col-sm-2 col-sm-offset-9">
        <button type="submit" class="btn btn-success"><span class="fa fa-fw fa-arrow-right"></span>&nbsp;&nbsp;Continue</button>
    </div>
</div>

}

Controller

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult AgreementTerms(AgreementTermViewModel aterms)
{
     if (ModelState.IsValid)
          return PartialView("_PreRegistration");

     return PartialView("_AgreementTerms", aterms);
}