SharePoint error The given assembly name or codebase System.ServiceModel.dll was invalid

I recently encountered a strange problem in the environment of SharePoint 2013, the day beforeSharePoint 2013 sites are still good. But suddenly the site reported page can ' t display 500 error:the given assembly name or codebase, ' C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel\v4.0_ 4.0.0.0__b77a5c561934e089\system.servicemodel.dll ', was invalid.

Description:An unhandled exception occurred during, the execution of the current Web request. Review the stack trace for more information about the error and where it is originated in the code.

Exception Details:System.IO.FileLoadException:The given assembly name or codebase, ' C:\Windows\Microsoft.Net\assembly\GAC_MSIL\ System.servicemodel\v4.0_4.0.0.0__b77a5c561934e089\system.servicemodel.dll ', was invalid.

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:

[fileloadexception:the given assembly name or codebase, ' C:\Windows\Microsoft.Net\assembly\GAC_MSIL\ System.servicemodel\v4.0_4.0.0.0__b77a5c561934e089\system.servicemodel.dll ', was invalid.] System.ServiceModel.Activation.ServiceHttpModule.BeginProcessRequest (Object sender, EventArgs E, AsyncCallback cb, Object extradata) +0 System.Web.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute () + 556 System.Web.HttpApplication.ExecuteStep (IExecutionStep step, boolean& completedsynchronously) +288

Version Information:Microsoft. NET Framework version:4.0.30319; ASP. version:4.0.30319.19051

The author spent a large half a day to investigate this problem, finally solve the problem. The solution to this problem is hereby written out, hoping to help a friend who has a similar problem.

The author later found that the service account in this environment was strangely removed from the local Administrators group. Seemingly not artificial, it could be the result of a Windows patch or domain security policy.

Regardless of how it was caused. It's good to know what the problem is. The author decisively adds the service account back to all apps and the local Administrators group of the WEB server.

Then restart all IIS and the problem is overcome.

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SharePoint Error The given assembly name or codebase System.ServiceModel.dll was invalid