SYMPTOMS
If you share an
XslTransform object from the
System.Xml.Xsl namespace between multiple threads, you may receive the following error message when you build your application:
System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
The call stack may appear as follows:
at System.Collections.ArrayListEnumeratorSimple.MoveNext()
at System.Xml.XPath.XsltFunction.SetXsltContext(XsltContext context)
at System.Xml.XPath.CompiledXpathExpr.SetContext(XmlNamespaceManager nsManager)
at System.Xml.Xsl.Processor.GetValueQuery(Int32 key)
at System.Xml.Xsl.Processor.ValueOf(ActionFrame context, Int32 key)
at System.Xml.Xsl.ValueOfAction.Execute(Processor processor, ActionFrame frame)
at System.Xml.Xsl.ActionFrame.Execute(Processor processor)
at System.Xml.Xsl.Processor.Execute()
at System.Xml.Xsl.XslTransform.Transform(IXPathNavigable input,XsltArgumentList args, TextWriter output)
This problem has only been seen to occur on computers that have more than one processor, although it is possible that this problem may also occur on a single processor computer.
RESOLUTION
To resolve this problem, obtain the latest service pack for Microsoft .NET Framework. For additional information, click the following article number to view the article in the
Microsoft Knowledge Base:
318836 INFO: How to Obtain the Latest .NET Framework Service Pack
: Apply this fix to systems that already have Microsoft .NET Framework with Service Pack 1 installed.
The English version of this fix should have the following file attributes or later:
Date Version Size File name
-------------------------------------------------------------
03-APR-2002 1.0.3705.223 1,294,336 bytes System.Xml.dll
WORKAROUND
To work around this problem, use the
lock statement (in Microsoft Visual C# .NET) or the
SyncLock...End SyncLock construct (in Microsoft Visual Basic .NET) to protect the use of the
Transform method. However, this workaround may incur an unacceptable performance penalty, depending on the design and the purpose of your application.
Another workaround that may offer better performance is to create a solution that implements a pool or a cache of
N+1
XslTransform objects, where
N is the number of processors on the computer.