メモ書き
XmlDocument xmlDoc = new XmlDocument();
XmlDeclaration xmlDecl = xmlDoc.CreateXmlDeclaration("1.0", "UTF-8", null);
xmlDoc.AppendChild(xmlDecl);
XmlElement rootElement = xmlDoc.CreateElement("DOC");
XmlElement firstElement = xmlDoc.CreateElement("FIRSTCHILD");
XmlElement secondElement = xmlDoc.CreateElement("SECONDCHILD");
XmlElement thirdElement = xmlDoc.CreateElement("THIRDCHILD");
secondElement.AppendChild(thirdElement);
firstElement.AppendChild(secondElement);
rootElement.AppendChild(firstElement);
xmlDoc.Save("xmlfilename.xml");
