Access to the temp directory is denied  Identity IIS APPPOOLamaxhouseware under which XmlSerializer is running does not have sufficient permission to access the temp directory  CodeDom will use the user account the process is using to do the compilation so if the user doesn�t have access to system temp directory you will not be able to compile  Use PathGetTempPath() API to find out the temp directory locationamaxhouseware.com