C# Xml

  document.Load(xmlpath);              //load xml by the absoult path

 XmlNodeList nodeList = document.GetElementsByTagName("nodetagname"); //get the nodelist of nodetagname

 XmlElement element = document.CreateElement("newnodename");  //create node 

 element.SetAttribute("attributename", "attributevalue");            //set attribute

nodeList[0].AppendChild(element);  //add the node to nodeList[0]