爱上MVC~MVC4模型验证可以放在前端_.NET_编程开发_程序员俱乐部

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MVC4.0推出后，在模型验证上有了一个新的改近，它支持前端验证，即在用户POST之前，如果验证失败，则Action(POST方式的）不会被执行，而直接停留在原视图，这对于用户体验是好的，它就类似于ajax验证一样，不会将原页重定向。

MVC4.0在view中引用了jqueryval文件后，即可实现客户端实时验证

@section Scripts {
  @Scripts.Render("~/bundles/jqueryval")
}

如果你不需要走JS方式验证，还是使用原来的POST方法后再进行验证的话，把上面那行删除即可，当然，MVC为我们提供的验证展示可能不是我们想要的，它往往会将“验证失败的提示信息”添加一个<span>然后为它加class，这可能并不是我们想要的，因为我们

的“错误提示”往往由前端开发人员提供的，所以，我们最需要的是“纯文字”的错误提示，现在，我把MVC的ValidationMessageFor扩展方法进行了新的扩展，我叫它ValidationMessageTextFor，它会将模型里的某个字段的验证错误的消息进行“纯文字”的输出，不

会有任何HTML标记，这才是我们所需要的，它也有不足，那就是目前并不支持前端实时模型验证！

ValidationMessageTextFor原代码如下，供大家学习与研究：

namespace System.Web.Mvc.Html
{
    /// <summary>
    /// MVC中对HtmlHelper扩展方法
    /// </summary>
    public static class MvcHtmlExtensions
    {
        /// <summary>
        /// 从ModelState中返回指定键对应的验证的错误消息
        /// </summary>
        /// <typeparam name="TModel"></typeparam>
        /// <typeparam name="TProperty"></typeparam>
        /// <param name="htmlHelper"></param>
        /// <param name="expression"></param>
        /// <returns></returns>
        public static MvcHtmlString ValidationMessageTextFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression)
        {

            var fieldName = ExpressionHelper.GetExpressionText(expression);

            var modelState = htmlHelper.ViewData.ModelState;
            if (!modelState.Keys.Contains(fieldName))
                return null;
            if (modelState[fieldName].Errors.Count == 0)
                return null;
            IList<string> errList = new List<string>();
            modelState[fieldName].Errors.ToList().ForEach(i =>
            {
                errList.Add(i.ErrorMessage);
            });
            return MvcHtmlString.Create(string.Join(",", errList));

        }
    }
}

现在输出的错误消息就是纯文字，如图

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