title: The type or namespace name 'Http' does not exist in the namespace 'System.Web'
body: <p>My Asp.net MVC action returns a view.  The action has no error, but when the view ends up with this error during compilation stage.  I don't know where this System.Web.Http.Data.Helpers is coming from.  I added a brand new empty MVC view from this action.  It got the same error.  This app uses MVC 5.2.3.0 and .NET Framework 4.5.2.  Does anyone know what the problem is?  Thank you.</p>
  
  <pre class="lang-html prettyprint-override"><code>Compilation Error 
    Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. 
  
   Compiler Error Message: CS0234: The type or namespace name 'Http' does not exist in the namespace 'System.Web' (are you missing an assembly reference?)
  
  Source Error:
  
  
  
  
  Line 26:     using System.Web.Optimization;
  Line 27:     using System.Web.Routing;
  Line 28:     using System.Web.Http.Data.Helpers;
  Line 29:     
  Line 30:     
  
  
  Source File: c:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\App_Web_accessrequest.cshtml.f4cc22dc.wyu-er3-.0.cs    Line: 28 
  
  
  
  Show Detailed Compiler Output:
  
  
  
  
  C:\Program Files (x86)\IIS Express&gt; "C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc.exe" /t:library /utf8output /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel\v4.0_4.0.0.0__b77a5c561934e089\System.ServiceModel.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.IdentityModel\v4.0_4.0.0.0__b77a5c561934e089\System.IdentityModel.dll" /R:"C:\WINDOWS\assembly\GAC_MSIL\Microsoft.ReportViewer.WinForms\10.0.0.0__b03f5f7f11d50a3a\Microsoft.ReportViewer.WinForms.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\Microsoft.CSharp\v4.0_4.0.0.0__b03f5f7f11d50a3a\Microsoft.CSharp.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel.Activities\v4.0_4.0.0.0__31bf3856ad364e35\System.ServiceModel.Activities.dll" /R:"C:\WINDOWS\assembly\GAC_MSIL\Microsoft.ReportViewer.DataVisualization\12.0.0.0__89845dcd8080cc91\Microsoft.ReportViewer.DataVisualization.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\17f2d89a\005843ef_e538d201\System.Spatial.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Web.ApplicationServices\v4.0_4.0.0.0__31bf3856ad364e35\System.Web.ApplicationServices.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Data.DataSetExtensions\v4.0_4.0.0.0__b77a5c561934e089\System.Data.DataSetExtensions.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\f90554c5\0033c11d_e638d201\Microsoft.Data.Services.Client.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\462aa9eb\00a1c9ec_4a3bd001\AjaxMin.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel.Web\v4.0_4.0.0.0__31bf3856ad364e35\System.ServiceModel.Web.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\Microsoft.VisualStudio.Web.PageInspector.Loader\v4.0_1.0.0.0__b03f5f7f11d50a3a\Microsoft.VisualStudio.Web.PageInspector.Loader.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\76c1f975\00d3e643_e638d201\Microsoft.Data.Edm.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\a4d0f7a8\00d9ab6a_b76bd201\Microsoft.WindowsAzure.Storage.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Web.WebPages.Deployment\v4.0_2.0.0.0__31bf3856ad364e35\System.Web.WebPages.Deployment.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Xml.Linq\v4.0_4.0.0.0__b77a5c561934e089\System.Xml.Linq.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\b3845a67\007c06f2_e72ed201\Microsoft.WindowsAzure.Configuration.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Web.DynamicData\v4.0_4.0.0.0__31bf3856ad364e35\System.Web.DynamicData.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel.Activation\v4.0_4.0.0.0__31bf3856ad364e35\System.ServiceModel.Activation.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Web.Services\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Web.Services.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System\v4.0_4.0.0.0__b77a5c561934e089\System.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_32\System.Web\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Web.dll" /R:"C:\WINDOWS\assembly\GAC_MSIL\Microsoft.SqlServer.Types\12.0.0.0__89845dcd8080cc91\Microsoft.SqlServer.Types.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Runtime.Serialization\v4.0_4.0.0.0__b77a5c561934e089\System.Runtime.Serialization.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Web.Extensions\v4.0_4.0.0.0__31bf3856ad364e35\System.Web.Extensions.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\f20c5ade\00a06763_c729cf01\itextsharp.dll" /R:"C:\WINDOWS\assembly\GAC_MSIL\Microsoft.ReportViewer.Common\10.0.0.0__b03f5f7f11d50a3a\Microsoft.ReportViewer.Common.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\016d1299\007175d9_0e55d001\EntityFramework.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.WorkflowServices\v4.0_4.0.0.0__31bf3856ad364e35\System.WorkflowServices.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\d7846dc9\007175d9_0e55d001\EntityFramework.SqlServer.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_32\System.EnterpriseServices\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.EnterpriseServices.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\App_global.asax.vinu2f-w.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\d672e3c6\005b0492_f23ad001\System.Web.Helpers.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Xml\v4.0_4.0.0.0__b77a5c561934e089\System.Xml.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\2bb4d80c\dbf24d75_18c3cf01\WebGrease.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel.DomainServices.Hosting\v4.0_4.0.0.0__31bf3856ad364e35\System.ServiceModel.DomainServices.Hosting.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\290cb87c\2f542505_6e78d201\CMT.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.ComponentModel.DataAnnotations\v4.0_4.0.0.0__31bf3856ad364e35\System.ComponentModel.DataAnnotations.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\ebdad562\431537fc_a4f7d001\AjaxControlToolkit.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\27d7eeaa\00ec03df_1b19cd01\Elmah.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\da0ee3a6\00e4da9d_b050d201\Microsoft.Azure.KeyVault.Core.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\5481e0d3\004f2fdb_02c6d101\Newtonsoft.Json.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\811e0cf8\490e9572_18c3cf01\System.Web.Optimization.dll" /R:"C:\WINDOWS\assembly\GAC_MSIL\Microsoft.ReportViewer.ProcessingObjectModel\12.0.0.0__89845dcd8080cc91\Microsoft.ReportViewer.ProcessingObjectModel.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\d2819038\0078360d_e321cf01\Glimpse.Mvc4.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Drawing\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Drawing.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\3c672836\00d2b709_acf3cf01\Glimpse.AspNet.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\Microsoft.Web.Infrastructure\v4.0_1.0.0.0__31bf3856ad364e35\Microsoft.Web.Infrastructure.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\3ce7727a\5d8f9942_a6f7d001\WebHelper.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\72c2229b\00c15643_f23ad001\System.Web.Mvc.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel.DomainServices.Server\v4.0_4.0.0.0__31bf3856ad364e35\System.ServiceModel.DomainServices.Server.dll" /R:"C:\Windows\Microsoft.NET\Framework\v4.0.30319\mscorlib.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\84cc9ff5\003729d0_00c9d101\MySql.Data.dll" /R:"C:\WINDOWS\assembly\GAC_MSIL\System.Data.SqlServerCe\4.0.0.0__89845dcd8080cc91\System.Data.SqlServerCe.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Web.WebPages.Deployment\v4.0_1.0.0.0__31bf3856ad364e35\System.Web.WebPages.Deployment.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\57169bbf\005b0492_f23ad001\System.Web.WebPages.Razor.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Configuration\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Configuration.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\1a877a98\0008f592_7daece01\Antlr3.Runtime.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\d3bafdd2\006926e2_e538d201\Microsoft.Data.OData.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\17aaa135\005b0492_f23ad001\System.Web.WebPages.Deployment.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Core\v4.0_4.0.0.0__b77a5c561934e089\System.Core.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_MSIL\System.Activities\v4.0_4.0.0.0__31bf3856ad364e35\System.Activities.dll" /R:"C:\WINDOWS\Microsoft.Net\assembly\GAC_32\System.Data\v4.0_4.0.0.0__b77a5c561934e089\System.Data.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\1034ad3d\005b0492_f23ad001\System.Web.WebPages.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\08931f20\007e29b7_f9ddd101\HtmlAgilityPack.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\442630b6\00fcae4b_f23ad001\System.Web.Razor.dll" /R:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\assembly\dl3\a665650f\00962356_ca90cf01\Glimpse.Core.dll" /R:"C:\WINDOWS\assembly\GAC_MSIL\Microsoft.ReportViewer.WebForms\10.0.0.0__b03f5f7f11d50a3a\Microsoft.ReportViewer.WebForms.dll" /out:"C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\App_Web_accessrequest.cshtml.f4cc22dc.wyu-er3-.dll" /D:DEBUG /debug+ /optimize- /w:4 /nowarn:1659;1699;1701;612;618 /debug:pdbonly /warnaserror-  "C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\App_Web_accessrequest.cshtml.f4cc22dc.wyu-er3-.0.cs" "C:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\App_Web_accessrequest.cshtml.f4cc22dc.wyu-er3-.1.cs"
  
  
  Microsoft (R) Visual C# Compiler version 4.6.1590.0
  
  for C# 5
  Copyright (C) Microsoft Corporation. All rights reserved.
  
  
  
  This compiler is provided as part of the Microsoft (R) .NET Framework, but only supports language versions up to C# 5, which is no longer the latest version. For compilers that support newer versions of the C# programming language, see http://go.microsoft.com/fwlink/?LinkID=533240
  
  c:\Users\myNetworkAccount\AppData\Local\Temp\1\Temporary ASP.NET Files\vs\cdda6d1e\b9ef792f\App_Web_accessrequest.cshtml.f4cc22dc.wyu-er3-.0.cs(28,22): error CS0234: The type or namespace name 'Http' does not exist in the namespace 'System.Web' (are you missing an assembly reference?)
  </code></pre>