'System.Web.WebPages.Html.HtmlHelper' does not contain a definition for 'DevExpress'

• Oct 06, 2023
• 2 minutes to read

This error can occur in the following cases:

• ASP.NET MVC 3 projects are upgraded to ASP.NET MVC 4 (or ASP.NET MVC 4 projects to ASP.NET MVC 5)

  Configure the “appSettings” and “assemblies” sections.

  MVC 3 to MVC 4:

  XML

  <appSettings>  
      <add key="webpages:Version" value="2.0.0.0" />  
      ...  
  </appSettings>  
  <system.web>  
      <compilation ...>  
          <assemblies>  
              ...  
              <add assembly="System.Web.Mvc, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />  
              <add assembly="System.Web.WebPages, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />  
              <add assembly="System.Web.Helpers, Version=2.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />  
          </assemblies>  
      </compilation>  
  </system.web>  
  

  See Also: Upgrading an ASP.NET MVC 3 Project to ASP.NET MVC 4

  MVC 4 to MVC 5:

  Follow steps listed in the following topic: How to Upgrade an ASP.NET MVC 4 and Web API Project to ASP.NET MVC 5 and Web API 2

• Areas are used.

  Copy DevExpress namespaces from the ~/Views/Web.config configuration file to ~/Areas/AREA_NAME/Web.config configuration file.

  For ASP.NET MVC 4:

  XML

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

  For ASP.NET MVC 3:

  ~/Areas/AREA_NAME/Web.config:

  XML

  <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" />  
              <add namespace="DevExpress.Utils" />  
              <add namespace="DevExpress.Web.ASPxClasses" />  
              <add namespace="DevExpress.Web.ASPxGridView" />  
              <add namespace="DevExpress.Web.ASPxGridView.Export" />  
              <add namespace="DevExpress.Web.ASPxEditors" />  
              <add namespace="DevExpress.Web.ASPxCallbackPanel" />  
              <add namespace="DevExpress.Web.ASPxMenu" />  
              <add namespace="DevExpress.Web.ASPxNavBar" />  
              <add namespace="DevExpress.Web.ASPxPopupControl" />  
              <add namespace="DevExpress.Web.ASPxRoundPanel" />  
              <add namespace="DevExpress.Web.ASPxSplitter" />  
              <add namespace="DevExpress.Web.ASPxTabControl" />  
              <add namespace="DevExpress.Web.ASPxTreeView" />  
              <add namespace="DevExpress.Web.ASPxUploadControl" />  
              <add namespace="DevExpress.Web.ASPxHtmlEditor" />  
              <add namespace="DevExpress.Web.ASPxSpellChecker" />  
              <add namespace="DevExpress.XtraCharts" />  
              <add namespace="DevExpress.XtraCharts.Web" />  
              <add namespace="DevExpress.XtraReports" />  
              <add namespace="DevExpress.XtraReports.UI" />  
              <add namespace="DevExpress.XtraReports.Web" />  
              <add namespace="DevExpress.XtraPivotGrid" />  
              <add namespace="DevExpress.Data.PivotGrid" />  
              <add namespace="DevExpress.Web.ASPxPivotGrid" />  
              <add namespace="DevExpress.Web.ASPxPivotGrid.Export" />  
              <add namespace="DevExpress.Web.Mvc" />  
              <add namespace="DevExpress.Web.Mvc.UI" />  
              <add namespace="DevExpress.XtraScheduler" />  
              <add namespace="DevExpress.XtraScheduler.Native" />  
              <add namespace="DevExpress.Web.ASPxScheduler" />  
          </namespaces>  
      </pages>  
  </system.web.webPages.razor>