what is the correct syntax to post an xml file to a web service.

ive tried

XmlDocument x = new XmlDocument();
x.LoadXml(XMLFile);

TxttoolsAddressbookServiceService myService = new TxttoolsAddressbookServiceService();
myService.Addressbook(x);

but this gives error on build -

cannot convert from 'System.Xml.XmlDocument' to 'TxtToolsService.AddressbookRequest'

also i tried converting the file to a series of bytes but get this error on build -

cannot convert from 'byte[]' to 'TxtToolsService.AddressbookRequest'

Whats the correct way to pass the xml data to the web service?