XML C# stream to String writing to Websphere MQ

ok question I have is how do I get this stream that I write to a string later in my code.

      // Here is the Code that reads the XML Payload Stream and Validates it to the correct Schema before sending the message forward.

                  System.Xml.XmlElement xe = payload.content[0].Any;
                  XmlDocument xmlDoc = xe.OwnerDocument;
                  xmlDoc.Schemas.Add(null, "http://localhost/wsTransport/ProcessCreditContract.xsd");
                  xmlDoc.Validate(delegate(object sender, ValidationEventArgs vargs)
                  {
                        Console.WriteLine("{0}: {1}", vargs.Severity, vargs.Message);
                  }, xe);

When I grab it here I can validate the xml against a .xsd file without issue. Now I want to take that same xml

and write it to a Websphere MQ Queue

something like this

MQMessage xmlPayload = new MQMessage();
                    XmlDocument xmlDoc = xe.OwnerDocument;
                    xmlPayload.WriteString(xmlPayload);

but I get the following error

------ Build started: Project: e:\projects\transWSEngine\, Configuration: Debug .NET ------
Validating Web Site
Building directory '/transWSEngine/App_Code/STARTransport2005ArkonaMS/'.

e:\projects\transWSEngine\App_Code\STARTransport2005ArkonaMS\service.cs(129,33): error CS0136: A local variable named 'xmlDoc' cannot be declared in this scope because it would give a different meaning to 'xmlDoc', which is already used in a 'parent or current' scope to denote something else
e:\projects\transWSEngine\App_Code\STARTransport2005ArkonaMS\service.cs(130,21): error CS1502: The best overloaded method match for 'IBM.WMQ.MQMessage.WriteString(string)' has some invalid arguments
e:\projects\transWSEngine\App_Code\STARTransport2005ArkonaMS\service.cs(130,44): error CS1503: Argument '1': cannot convert from 'IBM.WMQ.MQMessage' to 'string'
Validation Complete
========== Build: 0 succeeded or up-to-date, 1 failed, 0 skipped ==========

any help would be great as I am so close to getting this project finished just need to get over this last step.