Server Error in '/FoP' Application.

Collection was modified; enumeration operation may not execute.

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.InvalidOperationException: Collection was modified; enumeration operation may not execute.

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:


[InvalidOperationException: Collection was modified; enumeration operation may not execute.]
   System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) +60
   System.Collections.Generic.Enumerator.MoveNext() +14545127
   System.Linq.WhereEnumerableIterator`1.MoveNext() +74
   System.Collections.Generic.List`1..ctor(IEnumerable`1 collection) +475
   System.Linq.Enumerable.ToList(IEnumerable`1 source) +73
   FoPrintHandler.Helper.FoPCache.RemoveOldItemsFromCache() in C:\src\trunk\utilitytools\FopTransfo\FoPrintHandler\App_Code\Helper\FoPCache.cs:93
   FoPrintHandler.Helper.FoPCache.TryHandleRequestFromCache(HttpContext context, FileTypeHelperData ft, Parameters param) in C:\src\trunk\utilitytools\FopTransfo\FoPrintHandler\App_Code\Helper\FoPCache.cs:127
   FoPrintHandler.Converter.FoPImplementation.HandleApacheFoPGeneric(HttpContext context, Func`2 summonMemoryStream, FileTypeHelperData fth, Parameters param, Boolean useCache) in C:\src\trunk\utilitytools\FopTransfo\FoPrintHandler\App_Code\Converter\FoPImplementation.cs:198
   FoPrintHandler.Converter.FoPImplementation.HandleRequest(HttpContext context, Parameters param) in C:\src\trunk\utilitytools\FopTransfo\FoPrintHandler\App_Code\Converter\FoPImplementation.cs:110
   FoPrintHandler.FoPMeta.ProcessRequest(HttpContext context) in C:\src\trunk\utilitytools\FopTransfo\FoPrintHandler\FoPMeta.ashx.cs:29
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +542
   System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +75
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +93


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.8.4700.0