EF 事物Transaction简单操作

/// <summary>
        /// 申请提现
        /// </summary>
        /// <param name="userId">用户id</param>
        /// <param name="amount">提现金额</param>
        /// <returns></returns>
        public int ApplyTakeCash(int userId, decimal amount)
        { 
            if(IsExistUser(userId)) return -3; //用户不存在
            using (var context = new MediaDBContext())
            {
                var channelUser = context.ChannelUsers.FirstOrDefault(c => c.UserId == userId);
                if (channelUser == null) return -3;//用户不存在
                var purse = context.BackPurses.FirstOrDefault(c => c.OwnerId == channelUser.LeaderId);
                if (purse == null) return -2; //未绑定银行卡
                if (purse.Balance < amount) return -1; //余额不足
                using (var trans = context.Database.BeginTransaction())
                {
                    string description = string.Format("用户【{0}】申请提现【{1}】元金额", channelUser.User.Mobile, amount);
                    try
                    {
                        var model = new BackWithdrawCash
                        {
                            Amount = amount,
                            ApplicantId = 0,
                            PurseId = purse.Id,
                            Remark = description
                        };
                        //添加提现申请记录
                        context.BackWithdrawCashs.Add(model);
                        //减少提现额度
                        purse.Balance = purse.Balance - amount;
                        //提交
                        int res = context.SaveChanges();
                        if (res > 0)
                        {
                            //添加日志
                            AddOperateRecord(userId, channelUser.LeaderId, description+"成功");
                            //提交事物
                            trans.Commit();
                            return 1; //提交成功
                        }
                        //添加日志
                        AddOperateRecord(userId, channelUser.LeaderId, description + "失败");
                        return 0;//提交失败
                    }
                    catch (Exception ex)
                    {
                        Logger.Error("【TradingServices[ApplyTakeCash]】", ex);
                        //添加日志
                        AddOperateRecord(userId, channelUser.LeaderId, string.Format("【{0}】【{1}】",description,ex.Message));
                        //事物回滚
                        trans.Rollback();
                        return 0; //提交失败
                    }
                }
            }
        }