Error loading System.Web.WebPages.Deployment.dll

Question

User652541368 posted

I am seeing an error trying to run an ASP.Net application.  Site has multiple applications installed in the default web site.  Our app resides on the default web site and has its own app pool.  I see the following exception on first attempt to load an ASP.Net page:

Item has already been added. Key in dictionary: 'System.Web.WebPages.Deployment.dll'  Key being added: 'System.Web.WebPages.Deployment.dll'

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.ArgumentException: Item has already been added. Key in dictionary: 'System.Web.WebPages.Deployment.dll'  Key being added: 'System.Web.WebPages.Deployment.dll'

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.

Stack Trace:

[ArgumentException: Item has already been added. Key in dictionary: 'System.Web.WebPages.Deployment.dll'  Key being added: 'System.Web.WebPages.Deployment.dll']    System.Collections.Hashtable.Insert(Object key, Object nvalue, Boolean add) [phone]    WebApplication.Global.LoadReferencedAssemblies() +163    WebApplication.Global.Application_Start(Object sender, EventArgs e) +9   [HttpException (0x80004005): Item has already been added. Key in dictionary: 'System.Web.WebPages.Deployment.dll'  Key being added: 'System.Web.WebPages.Deployment.dll']    System.Web.HttpApplicationFactory.EnsureAppStartCalledForIntegratedMode(HttpContext context, HttpApplication app) [phone]    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): Item has already been added. Key in dictionary: 'System.Web.WebPages.Deployment.dll'  Key being added: 'System.Web.WebPages.Deployment.dll']    System.Web.HttpRuntime.FirstRequestInit(HttpContext context) [phone]    System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +159    System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) [phone]

 

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Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.18408