Entity framework 在EF Core中处理DbUpdateConcurrencyException

我使用的是EF Core 2.2.4。所有SQL表都有

timestamp

列。我有下面的方法，尝试为给定用户获取下一个工作订单。如果有多个用户同时竞争，我们可能会得到DbUpdateConcurrencyException，我使用重试逻辑处理它

注意，DBCntext作为

作用域

实例注入到服务的构造函数中

    public async Task<WorkOrder> GetNextOrder(int userID)
    {
        var maxTry = 3;            

        WorkOrder order = null;

            for (int i = 0; i < maxTry; i++)
            {
                order = await _dbContext.WorkOrder
                    .Where(o => o.UserID == null)
                    .OrderBy(o => o.CreatedDateTime)
                    .FirstOrDefaultAsync();

                if (order == null)
                {
                    break; //exit out of the loop
                }

                order.StatusID = (int)Statuses.InProgress;
                order.UserID = userID;
                order.AssignedDateTime = DateTime.UtcNow;
                try
                {
                    await _dbContext.SaveChangesAsync();
                    i = maxTry;
                }
                catch (DbUpdateConcurrencyException ex)
                {
                    // since mutiple users are compting for orders. We may get concurrency issue
                    // in such case retry to get next order                    
                    await _dbContext.Entry(order).ReloadAsync();
                    order = null;                        
                }
            }    

        return order;

    }

有没有办法在不将整个记录集加载到内存的情况下选择随机记录？

请看。请看。

        public async Task<WorkOrder> GetNextOrder(int userID)
        {
            var maxTry = 3;            

            WorkOrder order = null;
            using (var transaction = await _dbContext.Database.BeginTransactionAsync())
            {
                for (int i = 0; i < maxTry; i++)
                {
                    order = await _dbContext.WorkOrder
                    .Where(o => o.UserID == null)
                        .OrderBy(o => o.CreatedDateTime)
                        .FirstOrDefaultAsync();

                    if (order == null)
                    {
                        break; //exit out of the loop
                    }

                    order.StatusID = (int)Statuses.InProgress;
                    order.UserID = userID;
                    order.AssignedDateTime = DateTime.UtcNow;
                    try
                    {
                        await _dbContext.SaveChangesAsync();
                        i = maxTry;
                    }
                    catch (DbUpdateConcurrencyException ex)
                    {
                        // since mutiple users are compting for orders. We may get concurrency issue
                        // in such case retry to get next order                    
                        await _dbContext.Entry(order).ReloadAsync();
                        order = null;                        
                    }
                }

                transaction.Commit();
            }
            return order;

        }

 order = await _dbContext.WorkOrder
                    .Where(o => o.UserID == null)
                    .OrderBy(o => o.CreatedDateTime)
                    .TakeRandonRecord() ??