Webservice Exception

I’ve created web service by using below coding
[WebMethod(Description = “Echo Soap Request”)]

public XmlDocument EchoSoapRequest()
{
// Initialize soap request XML
XmlDocument xmlSoapRequest = new XmlDocument();

// Get raw request body
Stream receiveStream = HttpContext.Current.Request.InputStream;

// Move to begining of input stream and read
receiveStream.Position = 0;
using (StreamReader readStream = new StreamReader(receiveStream, Encoding.UTF8))
{
// Load into XML document
xmlSoapRequest.Load(readStream);
}

// Return
return xmlSoapRequest;
}

And I’m getting following error:

System.Xml.XmlException: Root element is missing.    at System.Xml.XmlTextReaderImpl.Throw(Exception e)    at System.Xml.XmlTextReaderImpl.ThrowWithoutLineInfo(String res)    at System.Xml.XmlTextReaderImpl.ParseDocumentContent()    at System.Xml.XmlTextReaderImpl.Read()    at System.Xml.XmlLoader.Load(XmlDocument doc, XmlReader reader, Boolean preserveWhitespace)    at System.Xml.XmlDocument.Load(XmlReader reader)    at System.Xml.XmlDocument.Load(TextReader txtReader)    at Recievingsoap.recieve.EchoSoapRequest() in C:\Users\kbvn189\Documents\Visual Studio 2010\Projects\Recievingsoap\Recievingsoap\recieve.asmx.cs:line 70 

If you have any idea get me soon. Urgent