Assigns the next document Id to this element. Use this method to generate an element Id, before it is registered in the specified document. Throws an expection if the element is already added to a document or the provided document is null. When an element Id is assigned to an element, it is a resposibility of the caller to ensure that the element is added to the elements subtree of the document for which the id was assigned.

public void AssignNextId( 
   NDocument document
)