Ответ 1
Вы можете создать XmlWriter непосредственно в XDocument:
XDocument doc = new XDocument();
using (var writer = doc.CreateWriter())
{
// write xml into the writer
var serializer = new DataContractSerializer(objectToSerialize.GetType());
serializer.WriteObject(writer, objectToSerialize);
}
Console.WriteLine(doc.ToString());