How to fix the error The type or name of the namespace "Linq" does not exist in the namespace "System",

Question

The ASP.NET MVC4 application contains the Helper.chtml file in the App_Code folder, which contains Razor helpers. After upgrading to Visual Studio Communitity, compile the error

Error CS0234 The type or namespace name 'Linq' does not exist in the namespace 'System' (are you missing an assembly reference?) C:\Users\user\AppData\Local\Temp\Temporary ASP.NET Files\admin\e209c0e0\c74032ba\Sources_App_Code\helper.cshtml.72cecc2a.cs 16 

It begins. The generated code contains:

 namespace ASP { using System; using System.Collections.Generic; using System.IO; using System.Linq; // Error occurs in this line using System.Net; using System.Web; using System.Web.Helpers; using System.Web.Security; using System.Web.UI; using System.Web.WebPages; using System.Web.WebPages.Html; #line 1 "C:\Web\Erp\App_Code\Helper.cshtml" using System.Web.Mvc; #line default #line hidden #line 2 "C:\Web\Erp\App_Code\Helper.cshtml" using System.Threading; #line default #line hidden #line 3 "C:\Web\Erp\App_Code\Helper.cshtml" using MyApp.Business; #line default #line hidden public class Helper : System.Web.WebPages.HelperPage { 

The error points to the line using System.Linq; .

How to fix it? Using ASP.NET4

I tried to add a link to System.Core for the project, but got an error that is already referenced. web.confing contains

 <compilation debug="true"> </compilation> 

I changed it to

 <compilation debug="true" targetFramework="4.0"> </compilation> 

according to the type or name of the Linq namespace does not exist in the namespace "System" and https://social.msdn.microsoft.com/Forums/en-US/c970ea3d-5238-4ec7-8859-e16b40dccd3d/the-type-or- namespace-name-linq-does-not-exist-in-the-namespace-systemare-you-missing-an? forum = linqprojectgeneral

but after that the compilation error will change to

 Error CS0234 The type or namespace name 'global_asax' does not exist in the namespace 'ASP' (are you missing an assembly reference?) 

which points to the code

  protected static ASP.global_asax ApplicationInstance { get { return ((ASP.global_asax)(Context.ApplicationInstance)); } } 

in the created helper.cshtml.72cecc2a.cs file.

How to fix this error?

Update

The relevant parts of web.config are:

 <?xml version="1.0" encoding="utf-8"?> <configuration> <system.data> <DbProviderFactories> <clear /> <add name="Npgsql Data Provider" invariant="Npgsql" support="FF" description=".Net Framework Data Provider for Postgresql Server" type="Npgsql.NpgsqlFactory, Npgsql" /> </DbProviderFactories> </system.data> <system.web> <httpModules> <remove name="RoleManager" /> </httpModules> <compilation debug="true"> </compilation> <customErrors mode="Off" /> <globalization uiCulture="auto" culture="auto" enableClientBasedCulture="true" /> <pages> <namespaces> <add namespace="MYApp.Business" /> <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.Optimization" /> <add namespace="System.Web.WebPages" /> </namespaces> </pages> </system.web> <runtime> <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"> <dependentAssembly> <assemblyIdentity name="WebGrease" publicKeyToken="31bf3856ad364e35" culture="neutral" /> <bindingRedirect oldVersion="0.0.0.0-1.6.5135.21930" newVersion="1.6.5135.21930" /> </dependentAssembly> <dependentAssembly> <assemblyIdentity name="Antlr3.Runtime" publicKeyToken="eb42632606e9261f" culture="neutral" /> <bindingRedirect oldVersion="0.0.0.0-3.5.0.2" newVersion="3.5.0.2" /> </dependentAssembly> </assemblyBinding> </runtime> </configuration> 

Answer 1

Try adding the System.Linq namespace to your default controller.