Unobtrusive validation doesn't work with Ajax.BeginForm

You need to add those 2 files in you Partial View even if it is already in the Shared/_Layout.cshtml:

<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.js")" type="text/javascript"></script>

Or place this in your Partial:

<script type="text/javascript" language=javascript>
    $.validator.unobtrusive.parse(document);
</script>

http://stackoverflow.com/questions/8927933/unobtrusive-validation-doesnt-work-with-ajax-beginform