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    Could not load file or assembly 'System.Web.Helpers' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Server Error in '/api' Application.

Could not load file or assembly 'System.Web.Helpers' 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.Helpers' 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.Helpers' could not be loaded.


=== Pre-bind state information ===
LOG: DisplayName = System.Web.Helpers
 (Partial)
WRN: Partial binding information was supplied for an assembly:
WRN: Assembly Name: System.Web.Helpers | Domain ID: 3
WRN: A partial bind occurs when only part of the assembly display name is provided.
WRN: This might result in the binder loading an incorrect assembly.
WRN: It is recommended to provide a fully specified textual identity for the assembly,
WRN: that consists of the simple name, version, culture, and public key token.
WRN: See whitepaper http://go.microsoft.com/fwlink/?LinkId=109270 for more information and common solutions to this issue.
LOG: Appbase = file:///C:/source/TDMS/TDMS.WebServices/
LOG: Initial PrivatePath = C:\source\TDMS\TDMS.WebServices\bin
Calling assembly : (Unknown).
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\source\TDMS\TDMS.WebServices\web.config
LOG: Using host configuration file: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet.config
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework64\v4.0.30319\config\machine.config.
LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind).
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework64/v4.0.30319/Temporary ASP.NET Files/api/8f8ef96b/51bdcfc3/System.Web.Helpers.DLL.
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework64/v4.0.30319/Temporary ASP.NET Files/api/8f8ef96b/51bdcfc3/System.Web.Helpers/System.Web.Helpers.DLL.
LOG: Attempting download of new URL file:///C:/source/TDMS/TDMS.WebServices/bin/System.Web.Helpers.DLL.
LOG: Using application configuration file: C:\source\TDMS\TDMS.WebServices\web.config
LOG: Using host configuration file: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet.config
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework64\v4.0.30319\config\machine.config.
LOG: Redirect found in application configuration file: 1.0.0.0 redirected to 3.0.0.0.
LOG: Post-policy reference: System.Web.Helpers, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework64/v4.0.30319/Temporary ASP.NET Files/api/8f8ef96b/51bdcfc3/System.Web.Helpers.DLL.
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework64/v4.0.30319/Temporary ASP.NET Files/api/8f8ef96b/51bdcfc3/System.Web.Helpers/System.Web.Helpers.DLL.
LOG: Attempting download of new URL file:///C:/source/TDMS/TDMS.WebServices/bin/System.Web.Helpers.DLL.
WRN: Comparing the assembly name resulted in the mismatch: Major Version
ERR: Failed to complete setup of assembly (hr = 0x80131040). Probing terminated.

Stack Trace: 


[FileLoadException: Could not load file or assembly 'System.Web.Helpers' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]

[FileLoadException: Could not load file or assembly 'System.Web.Helpers, Version=3.0.0.0, 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)]
   System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +0
   System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +234
   System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean forIntrospection) +108
   System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +25
   System.Reflection.Assembly.Load(String assemblyString) +34
   System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +49

[ConfigurationErrorsException: Could not load file or assembly 'System.Web.Helpers, Version=3.0.0.0, 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)]
   System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +772
   System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomainBinDirectory() +259
   System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai) +163
   System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +230
   System.Web.Compilation.BuildManager.GetPreStartInitMethodsFromReferencedAssemblies() +76
   System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +139
   System.Web.Compilation.BuildManager.ExecutePreAppStart() +176
   System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +882

[HttpException (0x80004005): Could not load file or assembly 'System.Web.Helpers, Version=3.0.0.0, 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)]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +579
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +112
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +712

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.6.1055.0

This is occuring in the TDMS.WebServices project, which is a .net 4.5 Web API 2.0. We also have a MVC5 project as well.

Deleting the .dll from the bin folder and compiling again fixes it. Rebuilding brings the DLL back and have to delete it.

Something is injecting the system.web.helpers.dll into the bin folder and I dont know what is causing it, but I suspect it may be related to the MVC project which does have a reference to System.Web.Helpers

Update:

This is the new error I got after redoing the reference:

Could not load file or assembly 'System.Web.Helpers' 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.Helpers' 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.Helpers' 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].

Stack Trace: 


[FileLoadException: Could not load file or assembly 'System.Web.Helpers' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]

[FileLoadException: Could not load file or assembly 'System.Web.Helpers, Version=3.0.0.0, 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)]
   System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +0
   System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks) +234
   System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, IntPtr pPrivHostBinder, Boolean forIntrospection) +108
   System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +25
   System.Reflection.Assembly.Load(String assemblyString) +34
   System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +49

[ConfigurationErrorsException: Could not load file or assembly 'System.Web.Helpers, Version=3.0.0.0, 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)]
   System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +772
   System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomainBinDirectory() +259
   System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai) +163
   System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +230
   System.Web.Compilation.BuildManager.GetPreStartInitMethodsFromReferencedAssemblies() +76
   System.Web.Compilation.BuildManager.CallPreStartInitMethods(String preStartInitListPath, Boolean& isRefAssemblyLoaded) +139
   System.Web.Compilation.BuildManager.ExecutePreAppStart() +176
   System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters, PolicyLevel policyLevel, Exception appDomainCreationException) +882

[HttpException (0x80004005): Could not load file or assembly 'System.Web.Helpers, Version=3.0.0.0, 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)]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +579
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +112
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +712
CuriousDeveloper
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    If it works again if you delete the DLL from the folder, it's most likely because it's loading it from the GAC. One of your projects is referencing this DLL and it puts a local copy in the bin folder when you compile, which causes it to break (bin folder has higher precedence). Check the GAC to see what version is stored there, then compile again and check the version that gets put in the folder. They are not the same. – JuanR Oct 12 '17 at 20:35
  • That seems to be the problem occurring, how do I fix it? I don't believe I can change the copy to local for the MVC project – CuriousDeveloper Oct 12 '17 at 20:54
  • What you need to do is reference the right version. Which one is higher? The GAC or the local reference? – JuanR Oct 12 '17 at 20:56
  • Well when I look at the output of `gacutil -l` I dont see system.web.helpers but I see a bunch of system.web stuff and they show 4.0.0.0 and the system.web.helpers.dll says Runtime Version v4.0.30319 and version 3.0.0.0 from visual studio. – CuriousDeveloper Oct 12 '17 at 21:20
  • What's the path of the reference within VS? (You can ommit the local stuff). – JuanR Oct 12 '17 at 21:24
  • Also, make sure to check if more than one project is referencing this assembly. – JuanR Oct 12 '17 at 21:25
  • The path of helpers is `C:\source\TDMS\packages\Microsoft.AspNet.WebPages.3.2.3\lib\net45\System.Web.Helpers.dll` A library project is referencing the MVC project, and then 10 projects reference the library. – CuriousDeveloper Oct 13 '17 at 01:21
  • Did you figure out if more than one project is referencing `System.Web.Helpers.dll`? – JuanR Oct 13 '17 at 13:08
  • I dont believe any other project has System.Web.helpers.dll in its references (but some projects have a reference to the project that does use it) – CuriousDeveloper Oct 13 '17 at 14:20
  • Good. Here is what I suggest you do: 1) Remove the reference from the project. 2) Close Visual Studio. 3) Delete the .SUO file (same folder as solution). 4) Open the solution again. 5) Add the reference to `System.Web.Hel‌​pers.dll` to the project again (make sure you are using the package path you posted before). 6) Recompile. 7) Run. Let me know how it goes! – JuanR Oct 13 '17 at 14:29
  • There was no .suo file next to solution but one of them inside one of the projects, so I deleted that. Did everything and didnt seem to fix anything, although I think the error message updated (see updated post). – CuriousDeveloper Oct 13 '17 at 20:03
  • Wait, something caught my eye. What architecture are you building for? x64? Make sure you use the right DLL. – JuanR Oct 13 '17 at 20:08
  • We dont specify an architecture (AnyCPU), but we could force 64 bit if we had to...ill double check DLL – CuriousDeveloper Oct 13 '17 at 20:37
  • I think you need to see this answer https://stackoverflow.com/questions/7668252/migrating-my-mvc-3-application-to-mvc-4 – AJ - Oct 31 '17 at 06:59
  • I think you need to see this answer https://stackoverflow.com/questions/7668252/migrating-my-mvc-3-application-to-mvc-4 – AJ - Oct 31 '17 at 07:00

2 Answers2

2

You're right about it being referred from MVC. System.Web.Helpers is normally a part of the package Microsoft.AspNet.WebPages which you can find on NuGet. In some runtime environments, it is installed stored in the GAC and therefore publicly available.

From the NuGet Console, run

Update-Package Microsoft.AspNet.WebPages

Make sure you have a redirect in web.config:

<dependentAssembly>
  <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
  <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
Dag Baardsen
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-1
Add the reference of System.Web.Helpers.dll file to your project,

and add below setting in web.config file

<dependentAssembly>
  <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
  <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
</dependentAssembly>
RiyajKhan
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