Changeset #5459 "#17754: Localizing validation attributes" caused client
validation fail. The problem is that unobtrusive html data attributes
are no longer rendered in html since Orchard 1.3.

Added lines in OrchardStarter.cs in 5459

// Register localized data annotations
ModelValidatorProviders.Providers.Clear();
ModelValidatorProviders.Providers.Add(new LocalizedModelValidatorProvider());

caused this. Here is the test.

ValidationController.cs

namespace Validation.Controllers
{
    using System.ComponentModel.DataAnnotations;
    using System.Web.Mvc;
    using Orchard.Themes;

    [Themed]
    public class ValidationController : Controller
    {
        public ActionResult Index()
        {
            return View(new ValidationEditModel());
        }
    }

    public class ValidationEditModel
    {
        [Required]
        public string Name { get; set; }
    }
}

Index.cshtml

@using Validation.Controllers
@model ValidationEditModel
@{
  HtmlHelper.ClientValidationEnabled = true;
  HtmlHelper.UnobtrusiveJavaScriptEnabled = true;
}
@using (Html.BeginForm())
{
  @Html.EditorForModel()
}

Html rendered in Orchard 1.2

<input class="text-box single-line" data-val="true" data-val-required="The Name field is required." id="Name" name="Name" type="text" value="" /> <span class="field-validation-valid" data-valmsg-for="Name" data-valmsg-replace="true">


Html rendered in Orchard 1.3

<input class="text-box single-line" id="Name" name="Name" type="text" value="" />