Xml文件修改后无法存储、大神来、神速结贴


<?xml version ="1.0"?>
<testNode>
    <nodeList name="First" location ="测试1">
        <nodes name="Third">测试数据1</nodes>
        <nodes name="Third">测试数据</nodes>
        <nodes name="Third">测试数据</nodes>
        <nodes name="Third">测试数据</nodes>
        <nodes name="Third">测试数据</nodes>
        <nodes name="Third">测试数据</nodes>
    </nodeList>
    <nodeList name="Second" location ="测试2">
        <nodes>测试数据01</nodes>
        <nodes>测试数据</nodes>
        <nodes>测试数据</nodes>
        <nodes>测试数据</nodes>
        <nodes>测试数据</nodes>
        <nodes>测试数据</nodes>
    </nodeList>
</testNode> string xml = @"<?xml version='1.0'?>
                      <testNode>
                       <nodeList name='First' location ='测试1'>
                       </nodeList>
                     </testNode> ";
        XmlDocument doc = new XmlDocument();//xml文档对象创建
        doc.LoadXml(xml);//xml文件读取        var list = doc.DocumentElement.SelectNodes("/testNode/nodeList[@name='First']"); //得到所有name=value的节点        foreach (XmlNode node in list)
        {
            var newNode = doc.CreateElement("SubNode");
            newNode.SetAttribute("name", "testValue");
            node.InsertAfter(newNode, node.LastChild);
        }
        string fileName = DateTime.Now.ToString("yyyyMMddhhmmss") + ".xml";
        using (XmlTextWriter writer = new XmlTextWriter(fileName, null))
        {
            writer.Formatting = Formatting.Indented;
            doc.Save(writer);
        }  问题：保存后无任何xml文件生成！