求助：文件服务器报错 Could not load file or assembly 'App_Web_wwd4gcop

求助：文件服务器一直好使，今天忽然报错如下，不知道是缺失了什么文件，谢谢~~~
WebHost failed to process a request.
Sender Information: System.ServiceModel.ServiceHostingEnvironment+HostingManager/30529585
Exception: System.ServiceModel.ServiceActivationException: The service '/K3CloudFileServer/FileService.svc' cannot be activated due to an exception during compilation. The exception message is: Could not load file or assembly 'App_Web_wwd4gcop, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. 系统找不到指定的文件。. ---> System.IO
.FileNotFoundException: Could not load file or assembly 'App_Web_wwd4gcop, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. 系统找不到指定的文件。
at System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection, Boolean suppressSecurityChecks)
at System.Reflection.RuntimeAssembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
at System.Reflection.Assembly.Load(String assemblyString)
at System.ServiceModel.Activation.ServiceHostFactory.CreateServiceHost(String constructorString, Uri[] baseAddresses)
at System.ServiceModel.ServiceHostingEnvironment.HostingManager.CreateService(String normalizedVirtualPath)
at System.ServiceModel.ServiceHostingEnvironment.HostingManager.ActivateService(String normalizedVirtualPath)
at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)
--- End of inner exception stack trace ---
at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)
at System.ServiceModel.ServiceHostingEnvironment.EnsureServiceAvailableFast(String relativeVirtualPath)
Process Name: w3wp
Process ID: 8048