Error: "Could not load file or assembly System.web.http.webhost file dependencies" when upgrading to SP14 Hotfix56


When attempting to upgrade to SP14 and/or Hotfix 56, the user receives the following error and the installation fails.

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 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=4.0.0.0, 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=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: 
 
 
[FileLoadException: 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 located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]
   Blackbaud.Web.Content.Portal.Global.RegisterWebAPIRoutes(String routePrefixName, String routePrefix) +0
   Blackbaud.Web.Content.Portal.Global.RegisterRoutes() +100
   Blackbaud.Web.Content.Portal.Global.Application_Start(Object sender, EventArgs e) +43
 
[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 located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]
   System.Web.HttpApplicationFactory.EnsureAppStartCalledForIntegratedMode(HttpContext context, HttpApplication app) +529
   System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +169
   System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +169
   System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +396
   System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +333
 
[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 located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +525
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +124
   System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +700

Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch 

Workaround: 

Add this to the web.config inside the ‘<runtime> <assemblyBinding>’ nodes:
 
   <dependentAssembly>
        <assemblyIdentity name="System.Web.Http.WebHost" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
     </dependentAssembly>
 
When making web.config changes, always backup the web.config before making changes. 
User-added image

Steps to Duplicate

1.  Apply patch
2. Attempt to open any BBIS page and receive error.
 
 

Environment

 Blackbaud CRM
 4.0
 4.0
 4.0.178.57
 BBIS
 4.0.178.0

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