How do I add xml document from one document into another document?

[winkimjr2]

I am having trouble adding xml document (CitationDocumentBatch) that is in this object objXMLInputDoc into another object objXMLCopyOfOriginalInputDoc. It should be added as a child of <soapenv:Body>

objXMLInputDoc object contains the following

CitationDocumentBatch schemaVersion="3:5" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
	<CitationDocument>
		<Citation>
	</CitationDocument>
</CitationDocumentBatch>

objXMLCopyOfOriginalInputDoc contains the following

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
	<soap:Header xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
	</soap:Header>
	<soapenv:Body>
	<!--Add CitationDocumentBatch here-->
	</soapenv:Body>
</soapenv:Envelope>

The result I want would be in objXMLCopyOfOriginalInputDoc which after I insert/add CitationDocumentBatch from objXMLInputDoc will look like this

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
	<soap:Header xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
	</soap:Header>
	<soapenv:Body>
	<CitationDocumentBatch schemaVersion="3:5" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
	<CitationDocument>
		<Citation>
	</CitationDocument>
</CitationDocumentBatch>
	</soapenv:Body>
</soapenv:Envelope>

Here is what I have tried.

objXMLCopyOfOriginalInputDoc.DocumentElement.SelectSingleNode("soap:Body", objXMLNameSpaceManager).AppendChild(objXMLInputDoc.SelectSingleNode("//CitationDocumentBatch"))

I am trying this in vb.net but I am getting an exception "The node to be inserted is from a different document context."

objXMLCopyOfOriginalInputDoc.DocumentElement.SelectSingleNode("soap:Body", objXMLNameSpaceManager).AppendChild(objXMLInputDoc.SelectSingleNode("//CitationDocumentBatch"))

Can someone help me with this? It might be very easy but I am not able to figure it out.