CS0234 Mvc does not exist in the System Web namespace

Question

I converted a ASP net 4 webform project to Asp net MVC4 according to Chapter 13 of the Professional ASP NET 3 5 MVC  by Scott Hanselmen  Phil Haack  and Rob Conery  Published by Wiley Publishing  Inc   ISBN  978-0-470-38461-9    I also followed this blog   Now I can add Controllers  Views  etc  All the references are set properly  No build errors   But upon launching the converted project  I got compilation errors   I have mvc3 installed on the same machine  I even changed the reference to that  It still complain   Could you help   Thanks   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  Mvc  does not exist in the namespace  System Web   are you missing an assembly reference    Source Error   Line 109              lt namespaces gt  Line 110                  lt add namespace  System Web Helpers   gt  Line 111                  lt add namespace  System Web Mvc   gt  Line 112                  lt add namespace  System Web Mvc Ajax   gt  Line 113                  lt add namespace  System Web Mvc Html   gt    Source File  c  Users Jon Documents Visual Studio 2012 Projects CMT Apps Branches 3 0 Web config    Line  111

User · Answer

Check your runtime tag inside the web config  and verify you have something like this declared    lt runtime gt       lt assemblyBinding xmlns  urn schemas-microsoft-com asm v1  gt         lt dependentAssembly gt           lt assemblyIdentity name  System Web Mvc  publicKeyToken  31bf3856ad364e35    gt           lt bindingRedirect oldVersion  0 0 0 0-4 0 0 0  newVersion  4 0 0 0    gt         lt  dependentAssembly gt         lt  runtime gt

User · Answer

You need to include the reference to the assembly System Web Mvc in you project   you may not have the System Web Mvc in your  C  Program Files  x86  Reference Assemblies Microsoft Framework NETFramework v4 0  So you need to add it and then to include it as reference to your projrect

User · Answer

None of previous answers worked for me   I noticed that my project was referencing another project using the System Web Mvc reference from the  NET Framework   I just deleted that assembly and added the  Microsoft AspNet Mvc  NuGet package and that fixed my problem

User · Answer

add Microsoft AspNet Mvc nuget package

User · Answer

This problem can happen when you deploy your web application to a server  so you must check if you already installed MVC3   Check if the folder C  Program Files Microsoft ASP NET ASP NET MVC 3 exists   If it doesn t exist  you need to install it from http   www microsoft com en-us download details aspx id 1491    If you wont to install you can add all DLLs locally in bin folder and add references to them this work fine if you host on server don t deploy ASP NET Web Pages or MVC3

User · Answer

I had this problem  but all the applications in IIS were broken when they had been working previously   None of the marked solutions helped me   The problem ended up being an extra copy of web config had been introduced to my root directory   I removed that file and problem solved

User · Answer

I had the same problem and I had solved it with   1 Right click to solution and click  Clean Solution    2 Click  References  folder in solution explorer and select the problem reference  in your case it seems System Web Mvc  and then right click and click  Properties    3 In the properties window  make sure that the  Copy Local  property is set to  True   This worked for me  Hope it works for someone else  Helpful Note  As it has mentioned in comments by  Vlad   If it is already set to True    Set it False   Set it True again Rebuild

User · Answer

I tried all these answers  even closed Visual Studio and deleted all bin directories   After starting it up again the MVC reference appeared to have a yellow exclamation mark on it  so I removed it and added it again   Now it works  without copy local

[asp.net-mvc] CS0234: Mvc does not exist in the System.Web namespace

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