asp.net-mvc-4 - ASP.NET MVC 4 Razor View 无法识别 HTML Helper 的下拉列表

Question

我正在尝试将下拉列表添加到强类型 Razor View 中。 ASP.Net MVC 4.0，Razor View 引擎版本 2.0.0.0

@using System;
@model SampleApp.Models.ServiceRequestModel

@{
  ViewBag.Title = "ServiceRequest";
}

@Html.DropDownListFor(m=>m.CategoryID, Model.Categories)

模型如下:

public class ServiceRequestModel
{
    public int ID { get; set; }
    public int CategoryID { get; set; }

    public SelectList Category { get; set; }
}

它总是在 CSHTML 文件中的智能感知中显示错误:

System.Web.WebPages.Html.HtmlHelper' does not contain a definition for 'DropDownListFor' and no extension method 'DropDownListFor' accepting a first argument of type 'System.Web.WebPages.Html.HtmlHelper' could be found (are you missing a using directive or an assembly reference?)

并且它给出了以下错误:

Error 3 The name 'model' does not exist in the current context

我已经检查了 View 文件夹中的 web.config:

<system.web.webPages.razor>
<host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
<pages pageBaseType="System.Web.Mvc.WebViewPage">
  <namespaces>
    <add namespace="System.Web.Mvc" />
    <add namespace="System.Web.Mvc.Ajax" />
    <add namespace="System.Web.Mvc.Html" />
    <add namespace="System.Web.Routing" />
  </namespaces>
</pages>

Answer 1

下面的配置代码行必须更改为 4.0.0.0

<host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, **Version=3.0.0.0**, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />

改为

<host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, **Version=4.0.0.0**, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />