public class ShowError
    {
        public ShowError(string key, string message)
        {
            Key = key;
            Message = message;
        }
        public string Key { get; set; }
        public string Message { get; set; }
    }

   public static class ModelStateExtensions
    {
        public static IEnumerable<ShowError> AllModelStateErrors(this ModelStateDictionary modelState)
        {
            var result = new List<ShowError>();
            //找到出錯(cuò)的字段以及出錯(cuò)信息
            var errorFieldsAndMsgs = modelState.Where(m => m.Value.Errors.Any())
                .Select(x => new {x.Key, x.Value.Errors});
            foreach (var item in errorFieldsAndMsgs)
            {
                //獲取鍵
                var fieldKey = item.Key;
                //獲取鍵對(duì)應(yīng)的錯(cuò)誤信息
                var fieldErrors = item.Errors
                    .Select(e => new ShowError(fieldKey, e.ErrorMessage));
                result.AddRange(fieldErrors);
            }
            return result;
        }
    }

   public class Student
    {
        public int Id { get; set; }
        [Required(ErrorMessage = "必填")]
        [StringLength(5, ErrorMessage = "長度1-5位")]
        public string Name { get; set; }
        [Required(ErrorMessage = "必填")]
        public int Age { get; set; }
        [Required(ErrorMessage = "必填")]
        [Range(typeof(Decimal), "0", "100", ErrorMessage = "{0} 必須是數(shù)字介于 {1} 和 {2}之間.")]
        public decimal Score { get; set; }
    }

   public class HomeController : Controller
    {
        public ActionResult Index()
        {
            return View(new Student());
        }
        [HttpPost]
        public ActionResult GetErrors(Student student)
        {
            if (ModelState.IsValid)
            {
                return Content("沒有錯(cuò)誤信息~~");
            }
            Response.StatusCode = 400;
            Response.TrySkipIisCustomErrors = true;
            var modelErrors = ModelState.AllModelStateErrors();
            return Json(modelErrors);
        }
    }

@model MvcApplication1.Models.Student
@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}
<h2>Index</h2>
@using (Html.BeginForm("GetErrors", "Home", FormMethod.Post, new {id = "addForm"}))
{
    @Html.TextBoxFor(m => m.Name)
    <br />
    @Html.TextBoxFor(m => m.Age)
    <br />
    @Html.TextBoxFor(m => m.Score)
    <br />
    <input type="button" id="up" value="提交" />
}
@section scripts
{
    <script type="text/javascript">
        $(function () {
            $('#up').on('click', function () {
                $.post('@Url.Action("GetErrors")', $('#addForm').serialize()).fail(function(error) {
                    var response = JSON.parse(error.responseText);
                    for (var i = 0; i < response.length; i++) {
                        var e = response[i];
                        var fieldKey = e.Key;
                        var message = e.Message;
                        console.log(fieldKey + ': ' + message);
                    }
                });
              
            });
        });
    </script>
}