/// <summary>
        /// 计算要插入、更新或删除的已修改对象的集,并执行相应命令以实现对数据库的更改
        /// </summary>
        /// <returns></returns>
        public async Task <int> SubmitChangesAsync()
        {
            int count = _dbQueryables.Count;

            if (count == 0)
            {
                return(0);
            }

            IDbConnection  conn  = null;
            IDbTransaction trans = null;

            try
            {
                List <string> sqlList = this.Resolve(false);
                conn = await _provider.CreateConnectionAsync(true);

                if (count > 1)
                {
                    trans = conn.BeginTransaction(System.Data.IsolationLevel.ReadCommitted);
                }

                var result = await _provider.ExecuteAsync(sqlList, trans);

                this.SetIdentity(result);

                if (trans != null)
                {
                    trans.Commit();
                }
            }
            catch
            {
                if (trans != null)
                {
                    trans.Rollback();
                }
                throw;
            }
            finally
            {
                if (trans != null)
                {
                    trans.Dispose();
                }
                if (conn != null)
                {
                    conn.Close();
                }
                if (conn != null)
                {
                    conn.Dispose();
                }
                this.Dispose();
            }

            return(count);
        }