Facing "Could not load file or assembly 'System.Web.Http.WebHost, Version=4.0.0.0, ' or one of its dependencies." [duplicate] - asp.net-mvc-4

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Could not load file or assembly 'System.Web.Http.WebHost, Version=4.0.0.0, Culture=neutral,PublicKeyToken=31bf3856ad364e35'
(8 answers)
Closed 5 years ago.
I am trying to deploy a MVC Web API solution on the server. The server has Windows 2012 R2 operating system. This is MVC 4 based Web API solution.
The server has .Net 4.0 framework installed. Except this server machine the solution has been deployed and working fine as expected. NOTE: those other machines has Visual Studio installed.
My issue here is - no matter whichever method I am applying, either solution itself or publish the solution, it is not working and giving below error.
Could not load file or assembly 'System.Web.Http.WebHost, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified
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.FileNotFoundException: Could not load file or assembly 'System.Web.Http.WebHost, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.
The stack trace says:
[FileNotFoundException: Could not load file or assembly 'System.Web.Http.WebHost, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.]
OSCARService.WebApiApplication.Application_Start() +0
[HttpException (0x80004005): Could not load file or assembly 'System.Web.Http.WebHost, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.]
System.Web.HttpApplicationFactory.EnsureAppStartCalledForIntegratedMode(HttpContext context, HttpApplication app) +544
System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +186
System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +172
System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +402
System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +343
[HttpException (0x80004005): Could not load file or assembly 'System.Web.Http.WebHost, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.]
System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +579
System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +112
System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +716
I tried finding this file (System.Web.Http.WebHost) in the framework directory but am unable to find this specific file.
I wonder Is this file necessarily required to be available physically?
I also tried setting System.Web.Http DLL to "CopyLocal='True'" but didn't work.
I already tried looking for similar situation/questions-answers here, but couldn't really get any direction.
I'd appreciate if anyone could provide direction here to my issue.

Answer 1

I fixed this by reinstalling the NuGet package, which corrects broken dependencies. From the package manager, try running this command
Update-Package Microsoft.AspNet.WebApi -reinstall

Answer 2

Check the bin folder of your deployed project. It should contain System.Web.Http.WebHost.dll. If this dll is in this folder, check the version. If it isn't 4.0.0.0, then you should deploy version 4.0.0.0. If you are using nuget packages, check your packages.config else check your web.config if you have the right version installed.
Hope this helps