Can't delete a row from an sqlite database.. any ideas?

I have an sqlite database which is displayed on a datagrid. I'm executing the query without any exceptions but the records are not deleted. I'm also having trouble to update the records too. any ideas? here is what I coded:

 private void EraseRow_Click(object sender, RoutedEventArgs e)
    {
        _conn.Open();
        SQLiteCommand cmd = new SQLiteCommand("Delete from Activity where RowID=5", _conn);

        cmd.ExecuteNonQuery(); 

        ActivitiesDataGrid.ItemsSource = _dataBase.updateDataGrid(_conn);
        _conn.Close();
    }

     public ObservableCollection<Activity> updateDataGrid(SQLiteConnection _sqlConnect)

        {

            List<Activity> _actList = new List<Activity>();

            SQLiteCommand cmd01 = new SQLiteCommand("SELECT * FROM Activity", _sqlConnect);

            SQLiteDataReader reader = cmd01.ExecuteReader();

            ObservableCollection<Activity> _activitiesList= new ObservableCollection<Activity>();

            while (reader.Read())
            {

                Activity _act = new Activity();

                _act.Name = reader.GetString(reader.GetOrdinal("Activity"));

                _act.Customer = reader.GetString(reader.GetOrdinal("ActivityCustomer"));

                string _actST = reader.GetString(reader.GetOrdinal("ActivityNature"));

                _act.Activitytpe = (ActivityType)Enum.Parse(typeof(ActivityType), _actST);

                string st = reader.GetString(reader.GetOrdinal("StartedAt"));

                _act.StartedAt = Convert.ToDateTime(st);

                string et = reader.GetString(reader.GetOrdinal("FinishedAt"));

                _act.EndedAt = Convert.ToDateTime(et);

                //string _ratio = reader.GetString(reader.GetOrdinal("ActivityRatio"));
                //_act.ActivityRatio = Convert.ToDouble(_ratio);
                _act.Notes = reader.GetString(reader.GetOrdinal("Notes"));

                string _hldy = reader.GetString(reader.GetOrdinal("Holiday"));

                _act.IsHoliday = Convert.ToBoolean(_hldy);

                _activitiesList.Add(_act);
            }

            return _activitiesList;
            //_adpt01.Fill(_tbl01);
            //dgrid.ItemsSource = _tbl01.DefaultView;
            //Disconnect(_sqlConnect);

        }