Передача параметра в oraclecommand в C#

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у меня с этим проблемы.
пожалуйста, загляните в этот код и помогите.
спасибо

Что я уже пробовал:

try
                {
                    string query = "SELECT uetc.team_codes, LPAD (papf.employee_number, 5, 0) staff_id,papf.full_name full_name, papf.email_address,LPAD (papf1.employee_number, 5, 0) supervisor_id,papf1.full_name supervisor_name, papf1.email_address, hl.location_code, SUBSTR (hl.location_code, 1, 3) branch_code, SUBSTR (hl.location_code, 6) branch_name, hl.loc_information15 region_name, hl.loc_information14 zone_name  FROM per_all_people_f papf, per_all_assignments_f paaf, per_grades pg, per_jobs pj, hr_locations_all hl, hr_all_organization_units haou, per_all_people_f papf1, per_all_assignments_f paaf1, per_grades pg1, per_jobs pj1, hr_locations_all hl1,  hr_all_organization_units haou1, ub_emp_team_codes_new uetc  WHERE papf.person_id = paaf.person_id AND papf.current_employee_flag = 'Y' AND SYSDATE BETWEEN papf.effective_start_date AND papf.effective_end_date AND paaf.primary_flag = 'Y'  AND papf.employee_number < 7000 AND papf.employee_number <> 00000 AND SYSDATE BETWEEN paaf.effective_start_date AND paaf.effective_end_date  AND paaf.grade_id = pg.grade_id(+) AND paaf.job_id = pj.job_id(+)  AND paaf.location_id = hl.location_id(+)  AND paaf.organization_id = haou.organization_id(+) AND paaf.supervisor_id = papf1.person_id(+)  AND papf1.person_id = paaf1.person_id(+) AND papf1.current_employee_flag(+) = 'Y' AND SYSDATE BETWEEN papf1.effective_start_date(+) AND papf1.effective_end_date(+) AND paaf1.primary_flag(+) = 'Y' AND SYSDATE BETWEEN paaf1.effective_start_date(+) AND paaf1.effective_end_date(+) AND paaf1.grade_id = pg1.grade_id(+) AND paaf1.job_id = pj1.job_id(+)  AND paaf1.location_id = hl1.location_id(+) AND paaf1.organization_id = haou1.organization_id(+) AND papf.person_id = uetc.person_id(+) AND uetc.person_id(+) = papf.person_id  AND papf.employee_number = @staff_id";
                    OracleCommand OraC = new OracleCommand(query, OracleConn);
                    OraC.CommandType = CommandType.Text;
                    OraC.Parameters.Add(new OracleParameter("@staff_id", OracleDbType.Varchar2)).Value = staffid;
                    //OraC.Parameters.Add(new OracleParameter("SESSION_ID", OracleDbType.Varchar2)).Value = SessionID;
                    //OraC.Parameters.Add(new OracleParameter("V_RESULT", OracleDbType.Varchar2, 32767)).Direction = ParameterDirection.Output;


                    //OracleDataReader dr = OraC.ExecuteNonQuery();
                    OracleDataReader dr = OraC.ExecuteReader();
                    while (dr.Read())
                    {
                        SupervisorEmail = dr["EMAIL_ADDRESS_1"].ToString();
                        StaffEmail = dr["EMAIL_ADDRESS"].ToString();
                        string id = dr["STAFF_ID"].ToString();
                    }

                }
                catch (Exception ex)
                {

                    ex.Message.ToString();
                }
                finally
                {
                    OracleConn.Close();
                } 

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