Could not load file or assembly 'System.Web.Http.WebHost...' or one of its dependencies. The module was expected to contain an assembly manifest

I have an MVC application that my customers deploy locally. It has worked for years.

I have a customer trying to load it in this environment:

• SERVER: Windows Small Business Server 2011 Standard
• IIS: 7.5
• .NET: 3.5.1 & 4.5

They are deploying as a subdomain, but receive this error:

Server Error in '/' Application.

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 
module was expected to contain an assembly manifest.

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.BadImageFormatException: 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 module was expected to contain an assembly manifest.

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=4.0.0.0, 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].

Stack Trace: 


[BadImageFormatException: 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 module was expected to contain an assembly manifest.]
site.MvcApplication.Application_Start() in f:\Users\{path}\site\Global.asax.cs:912

[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 module was expected to contain an assembly manifest.]
System.Web.HttpApplicationFactory.EnsureAppStartCalledForIntegratedMode(HttpContext 
context, HttpApplication app) +12864673
   System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, 
   HttpContext context, MethodInfo[] handlers) +175
   System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, 
   IntPtr appContext, HttpContext context) +304
   System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, 
   HttpContext context) +404
   System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +475

[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 module was expected to contain an assembly manifest.]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +12881540
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +159
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, 
   HttpContext context) +12722601

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.17929

I have tried

• copying the indicated dll from a working directory to no avail.
• checking the application pool information
• comparing settings between working sites and this one
• Many Google searches
• Fresh install of the application and IIS

Nothing we try seems to work. Ideas?

I deleted the bin folder, and rebuilt the application. Then I went through and made certain that the needed dlls were copied to local on publish and it works now.