判断xml中是否有指定内容的属性节点

        public bool HasNodesEqByClass(string className)
        {
            string tmpNodeName = "callfireswordwhenyouneedhelp";
            (PNode as XmlElement).SetAttribute(tmpNodeName, className);
            ///string tmpStr = PNode.OuterXml;
            XmlNodeList tmpNodes = PNode.SelectNodes("Item[@DataClass = ../@" + tmpNodeName + "]");
            return tmpNodes.Count > 0;
        }