System.IO.Exception error: "The requested operation cannot be performed on a file with a user-mapped section open."

c# xml ioexception
Bryan Denny picture Bryan Denny · Aug 19, 2009 · Viewed 69.4k times · Source

I received a very weird IOException when writing to an XML file:

System.IO.IOException: The requested operation cannot be performed on a file with a user-mapped section open.

   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share)
   at System.Xml.XmlTextWriter..ctor(String filename, Encoding encoding)
   at System.Xml.XmlDocument.Save(String filename)

The error happened when I called XmlDocument's Save(string) function.

Any ideas on what happened?

Answer

Richard picture Richard · Aug 19, 2009

Looks like another process had the file open using the file mapping (shared memory) APIs.

The find function in Process Explorer should be able to tell you.

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