Verion number XML 1.1 is invalid

Uri endpoint = new Uri("http://dbpedia.org");
            string query = "SELECT ?cat   WHERE { <http://dbpedia.org/resource/London> dcterms:subject ?cat .}";


       
            SparqlRemoteEndpoint source = new SparqlRemoteEndpoint(new Uri("http://dbpedia.org/sparql"), "http://dbpedia.org");
            SparqlResultSet resultSet = new SparqlResultSet();

       

            resultSet = source.=QueryWithResultSet(query);