Error loading XML in Xdocument

Question

I’m consuming a Webservice with the following code

WebRequest request = WebRequest.Create(link);

byte[] bytesToWrite = Encoding.ASCII.GetBytes(xml);

request.Method = "POST";
request.ContentLength = bytesToWrite.Length;
request.ContentType = "text/xml";
request.Headers.Add("SOAPAction", link);

Stream newStream = request.GetRequestStream();
newStream.Write(bytesToWrite, 0, bytesToWrite.Length);
newStream.Close();

HttpWebResponse response = (HttpWebResponse)request.GetResponse();
Stream dataStream = response.GetResponseStream();
StreamReader reader = new StreamReader(dataStream);

var xmlDoc = XDocument.Load(reader);

If I save the answer in a file I can read normally, var xmlDoc = XDocument.Load(@"C:\temp\Arquivo.xml");

If I try to charge straight

var xmlDoc = XDocument.Load(reader);

The following error appears :

System.xml.Xmlexception was unhandled Hresult=-2146232000 Linenumber=0 Lineposition=0 Message=Missing root element. Source=System.Xml Sourceuri="" Stacktrace: in System.xml.Xmltextreaderimpl.Throw(Exception e) in System.xml.Xmltextreaderimpl.Parsedocumentcontent() in System.xml.Xmltextreaderimpl.Read() in System.xml.Linq.XDocument.Load(Xmlreader Reader, Loadoptions options) in System.xml.Linq.XDocument.Load(Textreader textReader, Loadoptions options) in System.xml.Linq.XDocument.Load(Textreader textReader)