Could not load file or assembly System Web Http WebHost after published to Azure web site

Question

I created a web project and it runs well in Visual studio  However  I got the following error after published it to azurewebsites  What can cause the issue      Could not load file or assembly  System Web Http WebHost    Version 5 0 0 0  Culture neutral  PublicKeyToken 31bf3856ad364e35  or   one of its dependencies  The located assembly s manifest definition   does not match the assembly reference   Exception from HRESULT    0x80131040       Description  An unhandled exception occurred during the execution of   the current web request  Please review the stack trace for more   information about the error and where it originated in the code        Exception Details  System IO FileLoadException  Could not load file or   assembly  System Web Http WebHost  Version 5 0 0 0  Culture neutral    PublicKeyToken 31bf3856ad364e35  or one of its dependencies  The   located assembly s manifest definition does not match the assembly   reference   Exception from HRESULT  0x80131040       Source Error        An unhandled exception was generated during the execution of the   current web request  Information regarding the origin and location of   the exception can be identified using the exception stack trace below       Assembly Load Trace  The following information can be helpful to   determine why the assembly  System Web Http WebHost  Version 5 0 0 0    Culture neutral  PublicKeyToken 31bf3856ad364e35  could not be loaded       WRN  Assembly binding logging is turned OFF  To enable assembly bind   failure logging  set the registry value    HKLM Software Microsoft Fusion EnableLog   DWORD  to 1  Note  There   is some performance penalty associated with assembly bind failure   logging  To turn this feature off  remove the registry value    HKLM Software Microsoft Fusion EnableLog     The following is part of web config file       lt system web gt       lt customErrors mode  Off   gt       lt compilation debug  true  targetFramework  4 5    gt       lt httpRuntime targetFramework  4 5    gt       lt authentication mode  Forms  gt         lt forms loginUrl    Account Login  timeout  2880    gt       lt  authentication gt       lt pages gt         lt namespaces gt           lt add namespace  System Web Helpers    gt           lt add namespace  System Web Mvc    gt           lt add namespace  System Web Mvc Ajax    gt           lt add namespace  System Web Mvc Html    gt           lt add namespace  System Web Optimization    gt           lt add namespace  System Web Routing    gt           lt add namespace  System Web WebPages    gt         lt  namespaces gt       lt  pages gt     lt  system web gt     lt system webServer gt       lt validation validateIntegratedModeConfiguration  false    gt     lt handlers gt         lt remove name  ExtensionlessUrlHandler-ISAPI-4 0 32bit    gt         lt remove name  ExtensionlessUrlHandler-ISAPI-4 0 64bit    gt         lt remove name  ExtensionlessUrlHandler-Integrated-4 0    gt         lt add name  ExtensionlessUrlHandler-ISAPI-4 0 32bit  path      verb  GET HEAD POST DEBUG PUT DELETE PATCH OPTIONS  modules  IsapiModule  scriptProcessor   windir  Microsoft NET Framework v4 0 30319 aspnet isapi dll  preCondition  classicMode runtimeVersionv4 0 bitness32  responseBufferLimit  0    gt         lt add name  ExtensionlessUrlHandler-ISAPI-4 0 64bit  path      verb  GET HEAD POST DEBUG PUT DELETE PATCH OPTIONS  modules  IsapiModule  scriptProcessor   windir  Microsoft NET Framework64 v4 0 30319 aspnet isapi dll  preCondition  classicMode runtimeVersionv4 0 bitness64  responseBufferLimit  0    gt         lt add name  ExtensionlessUrlHandler-Integrated-4 0  path      verb  GET HEAD POST DEBUG PUT DELETE PATCH OPTIONS  type  System Web Handlers TransferRequestHandler  preCondition  integratedMode runtimeVersionv4 0    gt       lt  handlers gt  lt  system webServer gt     lt runtime gt       lt assemblyBinding xmlns  urn schemas-microsoft-com asm v1  gt         lt dependentAssembly gt           lt assemblyIdentity name  DotNetOpenAuth Core  publicKeyToken  2780ccd10d57b246    gt           lt bindingRedirect oldVersion  1 0 0 0-4 0 0 0  newVersion  4 1 0 0    gt         lt  dependentAssembly gt         lt dependentAssembly gt           lt assemblyIdentity name  DotNetOpenAuth AspNet  publicKeyToken  2780ccd10d57b246    gt           lt bindingRedirect oldVersion  1 0 0 0-4 0 0 0  newVersion  4 1 0 0    gt         lt  dependentAssembly gt         lt dependentAssembly gt           lt assemblyIdentity name  System Web Helpers  publicKeyToken  31bf3856ad364e35    gt           lt bindingRedirect oldVersion  1 0 0 0-2 0 0 0  newVersion  2 0 0 0    gt         lt  dependentAssembly gt         lt dependentAssembly gt           lt assemblyIdentity name  System Web Mvc  publicKeyToken  31bf3856ad364e35    gt           lt bindingRedirect oldVersion  1 0 0 0-4 0 0 0  newVersion  4 0 0 0    gt         lt  dependentAssembly gt         lt dependentAssembly gt           lt assemblyIdentity name  System Web WebPages  publicKeyToken  31bf3856ad364e35    gt           lt bindingRedirect oldVersion  1 0 0 0-2 0 0 0  newVersion  2 0 0 0    gt         lt  dependentAssembly gt         lt dependentAssembly gt           lt assemblyIdentity name  WebGrease  publicKeyToken  31bf3856ad364e35    gt           lt bindingRedirect oldVersion  0 0 0 0-1 5 2 14234  newVersion  1 5 2 14234    gt         lt  dependentAssembly gt         lt dependentAssembly gt           lt assemblyIdentity name  EntityFramework  publicKeyToken  b77a5c561934e089  culture  neutral    gt           lt bindingRedirect oldVersion  0 0 0 0-5 0 0 0  newVersion  5 0 0 0    gt         lt  dependentAssembly gt       lt  assemblyBinding gt     lt  runtime gt

User · Answer

I had the same problem in my Application.

System.web.http.webhost not found.

You just need to copy the system.web.http.webhost file from your main project which you run in Visual Studio and paste it into your published project bin directory.

After this it may show the same error but the directory name is changed it may be system.web.http. Follow same procedure as above. It will work after all the files are uploaded. This due to the nuget package in Visual Studio they download from the internet but on server it not able to download it.

You can find this file in your project bin directory.

User · Answer

In the case if  Copy Local  is already True  I find it sometimes to work if you remove the files where it has been published to and publish again   For example if you re using IIS  remove the websites and the contents of the directory to which they are published to  and publish again   There might be older versions of files at the destination  so to ensure you aren t using older versions  delete everything before publishing again

User · Answer

The dll is missing in the published  deployed environment   That is the reason why it is working in the local i e  Visual Studio but not in the Azure Website Environment   Just do Copy Local   true in the properties for the assembly System Web Http WebHost  and then do a redeploy  it should work fine

User · Answer

I met the same problem and I resolved it by setting CopyLocal to true for the following libs   System Web Http dll System Web Http WebHost dll System Net Http Formatting dll   I must add that I use MVC4 and NET 4

User · Answer

I removed the following entry from web config and it worked for me    lt dependentAssembly gt                   lt assemblyIdentity name  System Web Http WebHost  culture  neutral  publicKeyToken  31BF3856AD364E35    gt                   lt bindingRedirect oldVersion  0 0 0 0-65535 65535 65535 65535  newVersion  5 2 6 0    gt               lt  dependentAssembly gt

User · Answer

I m using vs2012 and i think the update KB2781514 changed some setting  All my System Web Http in my MVC4 project changed to false and i keeping received this message  I had changed the All file in this project in publish property but its not working  Finally I have to change Copy Local   true one by one and solved this problem

User · Answer

The dll is missing in the published  deployed environment   That is the reason why it is working in the local i e  Visual Studio but not in the Azure Website Environment   Just do Copy Local   true in the properties for the assembly System Web Http WebHost  and then do a redeploy  it should work fine    If you get the similar error i e  some other assembly missing  then make that assembly to copylocal true and redeploy  repeat this iteratively - if you are unsure of its dependencies

User · Answer

I was missing several DLLs  Even if I manually copied them to the directory the next time I published they would disappear   Each one was already set to Copy Locally in VS  The fix for me was to set each one to Copy Locally false   save  build then set each one to copy locally true   This time when I published all of the DLLs published correctly  Strange

User · Answer

For me it started working after selecting  Remove additional files at destination  in File publish options under settings on the publish dialog

User · Answer

If you have multiple projects in your solution and one of your projects fails to build because of this error then ensure you have installed the WebApi Core nuget package in that project  Simply adding a reference to the System Web Http does not help  you need to install the correct nuget package into that project   I had multiple projects in my solution and WebApi Core was already installed in another project  I referenced the System Web Http assembly by right-clicking and ticking the assembly from the list and it did not work on Azure  though locally it would build okay  I had to remove the manual reference and add the WebApi Core nuget package to each project that needed the assembly reference

User · Answer

Make sure the package version is equal across the solution  I just downgraded  amp  upgraded Microsoft AspNet Mvc package across the solution and the problem solved

User · Answer

I got the same error and I changed my version from 4 to 3 and it is solved    lt assemblyBinding xmlns  urn schemas-microsoft-com asm v1  gt       lt  -- Ensure correct version of MVC -- gt       lt dependentAssembly gt           lt assemblyIdentity name  System Web Mvc  publicKeyToken  31bf3856ad364e35   gt           lt bindingRedirect oldVersion  0 0 0 0-3 0 0 0  newVersion  3 0 0 0   gt       lt  dependentAssembly gt   lt  assemblyBinding gt

User · Answer

For me worked adding the following section to web config file    lt configuration gt           lt runtime gt                   lt dependentAssembly gt               lt assemblyIdentity name  System Web Http WebHost  publicKeyToken  31bf3856ad364e35  culture  neutral    gt               lt bindingRedirect oldVersion  0 0 0 0-5 1 0 0  newVersion  5 1 0 0    gt           lt  dependentAssembly gt               lt  runtime gt       lt  configuration gt    This example stands for MVC 5 1  Hope it will help someone to resolve such issue

User · Answer

This happened to me on VS2013 Update 5  ASP NET 4 5  under project type  Web Application  that includes MVC and Web API 2  Error happened right after creating the project and before adding any code  Adding the following configuration fix it for me  After resolving  System Web Helpers  issue two more similar errors surfaced for  System Web Mvc  and  System Web WebPages     lt runtime gt       lt assemblyBinding xmlns  urn schemas-microsoft-com asm v1  gt         lt dependentAssembly gt           lt assemblyIdentity name  System Web Helpers  publicKeyToken  31bf3856ad364e35  culture  neutral    gt           lt bindingRedirect oldVersion  0 0 0 0-2 0 0 0  newVersion  2 0 0 0    gt         lt  dependentAssembly gt         lt dependentAssembly gt           lt assemblyIdentity name  System Web Mvc  publicKeyToken  31bf3856ad364e35  culture  neutral    gt           lt bindingRedirect oldVersion  0 0 0 0-5 0 0 0  newVersion  5 2 3 0    gt         lt  dependentAssembly gt         lt dependentAssembly gt           lt assemblyIdentity name  System Web WebPages  publicKeyToken  31bf3856ad364e35  culture  neutral    gt           lt bindingRedirect oldVersion  0 0 0 0-3 0 0 0  newVersion  3 0 0 0    gt         lt  dependentAssembly gt

User · Answer

If you are still looking for an answer  try checking this question thread   It helped me resolve a similar problem   edit  The solution that helped me was to run Update-Package Microsoft AspNet WebApi -reinstall from the NugGet package manager  as suggested by Pathoschild  I then had to delete my  suo file and restart VS  as suggested by Sergey Osypchuk in this thread

[asp.net] Could not load file or assembly System.Web.Http.WebHost after published to Azure web site

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