HiLoGenerator生成id

using System.Linq;

namespace Product.Host
{
    public class HiLoGenerator
    {
        private const int HiLoIncrement = 10;
        private int _sequenceId = -1;
        private int _remainningLoIds = 0;
        private object SequenceLock = new object();

        public int GetNextSequenceValue(ProductDbContext db)
        {
            lock (SequenceLock)
            {
                if (_remainningLoIds == 0)
                {
                    var rawQuery = db.Database.SqlQuery<long>("SELECT NEXT VALUE FOR Product_HiLo;");
                    _sequenceId = (int)rawQuery.Single();
                    _remainningLoIds = HiLoIncrement - 1;
                    return _sequenceId;
                }
                else
                {
                    _remainningLoIds--;
                    return ++_sequenceId;
                }
            }
        }
    }
}

sql

CREATE SEQUENCE [dbo].[Product_HiLo] 
 AS [bigint]
 START WITH 1
 INCREMENT BY 10
 MINVALUE -9223372036854775808
 MAXVALUE 9223372036854775807
 CACHE