public List<District> GetAllDistrict()
        {
            var cursor = db.abc ();
            List<District> list = new List<District> ();
            list.Add (new District {
                name = "Chọn quận",
            });
            list [0].addChild (new Ward{ name = "Chọn phường" });
            if (cursor.MoveToFirst ()) {
                for (int i = 0; i < cursor.Count; i++) {
                    int id = cursor.GetInt (cursor.GetColumnIndex (District.ID_COLUMN));
                    string name = cursor.GetString (cursor.GetColumnIndex (District.NAME_COLUMN));
                    District item = new District{ id = id, name = name };

                    var cursorWard = db.GetWardFromDistrictID (id);
                    if (cursorWard.MoveToFirst ()) {

                        item.addChild (new Ward{ name = "Chọn phường" });
                        for (int j = 0; j < cursorWard.Count; j++) {
                            item.addChild (
                                new Ward {
                                    id = cursorWard.GetInt (cursor.GetColumnIndex (Ward.ID_COLUMN)),
                                    name = cursorWard.GetString (cursor.GetColumnIndex (Ward.NAME_COLUMN)),
                                    districtParent = item
                                });
                            cursorWard.MoveToNext ();
                        }

                    } else {
                        item.addChild (new Ward{ name = "Không tìm thấy" });
                    }
                    list.Add (item);
                    cursor.MoveToNext ();
                }
                return list;
            }
            return list;
        }