System.InvalidOperationException: This document already has a 'DocumentElement' node.
   at System.Xml.XmlDocument.IsValidChildType(XmlNodeType type)
   at System.Xml.XmlNode.AppendChild(XmlNode newChild)
   at tfox.CommonLibrary.CommonClass.GetSysXmlNode(String NodeName)
   at tfox.fenzhan.NGenerateSub.GetData(String entity, String filter)
   at tfox.fenzhan.NGenerateSub.BindData(Match match, StringBuilder sb)
   at tfox.fenzhan.NGenerateSub.BindData(StringBuilder sb, String rootPath, String template)
   at tfox.fenzhan.NGenerateSub.GenerateProList(String rootPath, String template, String typeid1, String id, String city, String py, String page)