public class MVCHelper

    {

        //有 两 个ModelStateDictionary类，别弄混乱了要使用 System.Web.Mvc 下的

        //如果添加引用中找不到System.Web.MVC，那么可以用nuget安装：

        //Install-Package Microsoft.AspNet.Mvc

        public static string GetValidMsg(System.Web.Mvc.ModelStateDictionary modelState)

        {

            StringBuilder sb = new StringBuilder();

            foreach (var key in modelState.Keys)

            {

                if (modelState[key].Errors.Count <= )

                    continue;

                sb.AppendFormat(" 属性【{0}】错误：", key);

                foreach (var modelError in modelState[key].Errors)

                {

                    sb.AppendLine(modelError.ErrorMessage);

                }

            }

            return sb.ToString();

        }

        public static string RemoveQueryString(NameValueCollection nvc, string name)

        {

            NameValueCollection newNvc = new NameValueCollection(nvc);

            newNvc.Remove(name);

            return ToQueryString(newNvc);

        }

        public static string UpdateQueryString(NameValueCollection nvc, string name, string value)

        {

            NameValueCollection newNvc = new NameValueCollection(nvc);

            if (newNvc.AllKeys.Contains(name))

                newNvc[name] = value;

            else

                newNvc.Add(name, value);

            return ToQueryString(newNvc);

        }

        private static string ToQueryString(NameValueCollection newNvc)

        {

            StringBuilder sb = new StringBuilder();

            foreach (var key in newNvc.AllKeys)

            {

                string value = newNvc[key];

                //EscapeDataString就是对特殊字符进行uri编码

                sb.AppendFormat("{0}={1}&", key, Uri.EscapeDataString(value));

            }

            return sb.ToString().Trim('&');//去掉最后一个多余的&

        }

        //生成XXX的静态html页面的 方法

        public static string RenderViewToString(ControllerContext context, string viewPath, object model = null)

        {

            ViewEngineResult viewEngineResult = ViewEngines.Engines.FindView(context, viewPath, null);

            if (viewEngineResult == null)

                throw new FileNotFoundException("View" + viewPath + "cannot be found.");

            var view = viewEngineResult.View;

            context.Controller.ViewData.Model = model;

            using (var sw = new StringWriter())

            {

                var ctx = new ViewContext(context, view, context.Controller.ViewData, context.Controller.TempData, sw);

                view.Render(ctx, sw);

                return sw.ToString();

            }

        }

    }