score:3

Accepted answer
titles = from nametag in xml.element("empfieldsmap").elements("field")
         let insert = nametag.element("name").attribute("insert")
         where insert == null || (bool)insert
         select nametag.element("name").value;

score:1

titles = (from nametag in xml.element("empfieldsmap").elements("field"))
         .where ( el=> (el.attribute("insert").value.equals("true") )  ||
                        (el.attribute("update").value.equals("false") )
         select(f => new 
            {
                text = nametag.element("name").value
             });

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