i have a problem when i try to export from sql mobile to xml .I keep getting this error Cannot generate an updatable cursor for the query because there is no updatable column [ Cursor Option = 2 ].

Code:
 StreamWriter sw = File.CreateText(@"\Program Files\ContorPDA\Aparate.xml");
                string result = string.Empty;
                string res = string.Empty;
                result += "<?xml version='1.0'?>" + "\r\n";
                result += "<Aparate>" + "\r\n";
                sw.Write(result);
                SqlCeCommand cmd = Biblio.pCon.CreateCommand();
                cmd.CommandText = "SELECT  '<Aparat Id=\"'+ CONVERT(nvarchar,id) + '\" Denumire=\"' + Denumire + " +
                                   " '\"  NumarCitire=\"' + NumarCitire + " +
                                   " '\" DataCitire=\"' + CONVERT(nvarchar,DataCitire) + " +
                                   " '\" ContorGeneralInitial=\"' + ContorGeneralInitial + " +
                                   " '\" ContorGeneralFinal=\"' + ContorGeneralFinal +'\" Partener=\"' + Partener +  '\" >', Aparat.id" +
                                   " FROM Aparat ";
                SqlCeResultSet scrs = cmd.ExecuteResultSet(ResultSetOptions.Scrollable);
               
                while (scrs.Read())
                {
                    result = String.Empty;
                    result += scrs.GetValue(0) + "\r\n";
               
                    SqlCeCommand cmdP = Biblio.pCon.CreateCommand();
                                   
                     cmdP.CommandText = "SELECT '<Pozitie Id=\"' + CONVERT(nvarchar,id) + '\" id_aparat=\"' + CONVERT(nvarchar,id_aparat) + " +
                        " '\" ContorInitial=\"' + ContorInitial + '\" ContorFinal=\"' +ContorFinal + '\" Produs=\"' + Produs +'\"/>' FROM Prodaparat WHERE Prodaparat.id_aparat=" + scrs.GetValue(1);
                
                    SqlCeResultSet scrsP = cmdP.ExecuteResultSet(ResultSetOptions.Scrollable);
                    result += "\t" + "<Pozitii>" + "\r\n\t";
                    while (scrsP.Read())
                    {
                        result = String.Empty;
                        result += "\t" + scrsP.GetValue(0) + "\r\n\t";
                    }
                
                    result += "</Pozitii>" + "\r\n";
                    result += "</Aparat>" + "\r\n";
                    sw.Write(result);

                }
                result = "</Aparate>" + "\r\n";
                sw.Write(result);
                sw.Close();
error at the line : SqlCeResultSet scrsP = cmdP.ExecuteResultSet(ResultSetOptions.Scrollable);

what could it be?