Insert in c# using npgsql

When I'm trying to execute an insert query with npgsqlcommand to postgres in c#, the execution of the program is suspend to cmd.ExecuteNonQuery(); Here's my code

public void Insert(Mouvement mvt)
    {
        NpgsqlConnection conn = null;
        NpgsqlCommand cmd = null;
        try
        {
            conn = UtilDB.GetConnection();
            String sql = "INSERT INTO MOUVEMENT(ID_AERONEF,ID_PF,ID_ESCALE,DATE,SENS,NVOL,PISTE,BLOC,PAXC,PAXY,PAXBB,PAXEXO," +
                "TRANSITDIRECT,TRANSITRI,TRANSITRRLC,CONTINU,PN,FRETPAYANT,FRETGRATUIT,BAGAGE,POSTE,MODE,BALISAGE,OBSERVATION) "+
                "VALUES (:id_aeronef,:id_pf,:id_escale,:date,:sens,:nvol,:piste,:bloc,:paxc,:paxy,:paxbb,:paxexo," +
                ":transitdirect,:transitri,:transitrrlc,:continu,:pn,:fretpayant,:fretgratuit,:bagage,:poste,:mode,:balisage,:observation)";
            conn.Open();
            cmd = new NpgsqlCommand(sql, conn);
            cmd.Parameters.Add("id_aeronef", mvt.Aeronef.Id);
            cmd.Parameters.Add("id_pf", mvt.Plateforme.Id);
            cmd.Parameters.Add("id_escale", mvt.Escale.Id);
            cmd.Parameters.Add("date", mvt.Date);
            cmd.Parameters.Add("sens", mvt.Sens);
            cmd.Parameters.Add("nvol", mvt.Nvol);
            cmd.Parameters.Add("piste", mvt.Piste);
            cmd.Parameters.Add("bloc", mvt.Bloc);
            cmd.Parameters.Add("paxc", mvt.PaxC);
            cmd.Parameters.Add("paxy", mvt.PaxY);
            cmd.Parameters.Add("paxbb", mvt.PaxBB);
            cmd.Parameters.Add("paxexo", mvt.PaxExo);
            cmd.Parameters.Add("transitdirect", mvt.TransitDirect);
            cmd.Parameters.Add("transitri", mvt.TransitRI);
            cmd.Parameters.Add("transitrrlc", mvt.TransitRRLC);
            cmd.Parameters.Add("continu", mvt.Continu);
            cmd.Parameters.Add("pn", mvt.Pn);
            cmd.Parameters.Add("fretpayant", mvt.FretPayant);
            cmd.Parameters.Add("fretgratuit", mvt.FretGratuit);
            cmd.Parameters.Add("bagage", mvt.Bagage);
            cmd.Parameters.Add("poste", mvt.Poste);
            cmd.Parameters.Add("mode", mvt.Mode);
            cmd.Parameters.Add("balisage", mvt.Balisage);
            cmd.Parameters.Add("observation", mvt.Observation);
            cmd.Prepare();
            cmd.CommandType = CommandType.Text;
            cmd.ExecuteNonQuery();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            if(cmd!=null) cmd.Dispose();
            if(conn!=null) conn.Close();
        }
    }