System.Web.MVC.HtmlHelper Ambiguous Issue

Question

I have an asp.net mvc application. Inside my views, I can't use extension methods like LabelFor<>, TextboxFor<>. I have got error like this:

(Ambiguous name -- choose from the following:) System.Web.WebPages.Html.HtmlHelper System.Web.Mvc.HtmlHelper

How can I fix this?

EDIT: My Views/Web.Config:

<?xml version="1.0"?>

<configuration>
  <configSections>
    <sectionGroup name="system.web.webPages.razor" type="System.Web.WebPages.Razor.Configuration.RazorWebSectionGroup, System.Web.WebPages.Razor, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
      <section name="host" type="System.Web.WebPages.Razor.Configuration.HostSection, System.Web.WebPages.Razor, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" />
      <section name="pages" type="System.Web.WebPages.Razor.Configuration.RazorPagesSection, System.Web.WebPages.Razor, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" />
    </sectionGroup>
  </configSections>

  <system.web.webPages.razor>
    <host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=5.1.0.0, 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" />
        <add namespace="System.Web.Optimization"/>
      </namespaces>
    </pages>
  </system.web.webPages.razor>

  <appSettings>
    <add key="webpages:Enabled" value="false" />
  </appSettings>

  <system.web>
    <httpHandlers>
      <add path="*" verb="*" type="System.Web.HttpNotFoundHandler"/>
    </httpHandlers>

    <!--
        Enabling request validation in view pages would cause validation to occur
        after the input has already been processed by the controller. By default
        MVC performs request validation before a controller processes the input.
        To change this behavior apply the ValidateInputAttribute to a
        controller or action.
    -->
    <pages
        validateRequest="false"
        pageParserFilterType="System.Web.Mvc.ViewTypeParserFilter, System.Web.Mvc, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"
        pageBaseType="System.Web.Mvc.ViewPage, System.Web.Mvc, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"
        userControlBaseType="System.Web.Mvc.ViewUserControl, System.Web.Mvc, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
      <controls>
        <add assembly="System.Web.Mvc, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" namespace="System.Web.Mvc" tagPrefix="mvc" />
      </controls>
    </pages>
  </system.web>

  <system.webServer>
    <validation validateIntegratedModeConfiguration="false" />

    <handlers>
      <remove name="BlockViewHandler"/>
      <add name="BlockViewHandler" path="*" verb="*" preCondition="integratedMode" type="System.Web.HttpNotFoundHandler" />
    </handlers>
  </system.webServer>
</configuration>

Main web.config:

<system.web.webPages.razor>
    <host factoryType="System.Web.Mvc.MvcWebRazorHostFactory, System.Web.Mvc, Version=5.1.0.0, 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.Optimization" />
        <add namespace="System.Web.Routing" />
      </namespaces>
    </pages>
  </system.web.webPages.razor>

system.web/pages/namespaces:

<system.web>
    <httpRuntime targetFramework="4.5" />
    <compilation debug="true" targetFramework="4.5.1" />
    <pages>
      <namespaces>
        <add namespace="System.Web.Helpers" />
        <add namespace="System.Web.Mvc" />
        <add namespace="System.Web.Mvc.Ajax" />
        <add namespace="System.Web.Mvc.Html" />
        <add namespace="System.Web.Routing" />
        <add namespace="System.Web.WebPages" />
        <add namespace="System.Web.Optimization" />
      </namespaces>
    </pages>
  </system.web>

Can you show the <system.web/pages/namespaces> section in the main Web.Config? — haim770
Are you using a custom html helper in your view. Sounds like you have referenced System.Web.WebPages.Html as well as System.Web.Mvc.Html somewhere. — user3559349
@StephenMuecke that's exactly my problem. I need to use System.Web.Mvc.Html reference, but somehow System.Web.WebPages.Html reference comes out. — Umut Derbentoğlu

Gareth Hopkins Gareth Hopkins · Accepted Answer · 2014-11-27T15:20:06

I can't comment yet (under 50 reputation) but just to add to the conversation it looks like you're referencing 4.0.0.0 and 5.1.0.0 of System.Web.Mvc, not sure that's causing the problem but make sure you've got binding redirects or change the version numbers to the version you have referenced. I've had multiple problems stemming from the various Mvc/WebPages dll versions.

<dependentAssembly>
  <assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" />
  <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
<dependentAssembly>
  <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
  <bindingRedirect oldVersion="1.0.0.0-5.1.0.0" newVersion="5.1.0.0" />
</dependentAssembly>

Thanks, Gareth

System.Web.MVC.HtmlHelper Ambiguous Issue

1 Answers