XmlWriterSettings, xmltextwwriter, XmlWriter不格式化输出?!没有新行，没有缩

在VS2008中使用。net 3.5 SP1，我有一个XmlDocument，并尝试将其写入file:

using (XmlTextWriter tw = new XmlTextWriter(outXmlFileName, System.Text.Encoding.UTF8))
{
    tw.Formatting = Formatting.Indented;
    tw.Indentation = 3;
    tw.IndentChar = ' ';
    tw.QuoteChar = '''';
    doc.Save(tw);
}

和

XmlWriterSettings settings = new XmlWriterSettings();
settings.Indent = true;
using (XmlWriter writer = XmlWriter.Create(outXmlFileName, settings))
{
    doc.Save(writer);
}

从文档http://msdn.microsoft.com/en-us/library/kkz7cs0d.aspx中不清楚的是，如果我应该使用。net 2之上的XmlWriter.Create()，无论如何都没有方法格式化输出!我只得到XmlDocument实例中的内容:

<?xml version='1.0' encoding='utf-8'?>
<root>
<node1  />
<node2 value='Data' />
<node3 value='ID' /><node4><item>
<from value='1 Jan 1870' />
<id value='PF' />
<to value='1 Jan 1940' /></item></node4>
</root>

我怎么能整理我的XML之前写它的文件从。net ?

            XmlWriterSettings settings = new XmlWriterSettings(); // http://msdn.microsoft.com/en-us/library/kkz7cs0d(VS.85).aspx
            settings.Indent = true;
            XmlDocument doc2 = new XmlDocument();
            doc2.LoadXml(doc.OuterXml);
            using (XmlWriter writer = XmlWriter.Create(outXmlFileName, settings))
            {
                doc2.Save(writer);
            }