SQL事务

            string connstr = "";
            using (SqlConnection conn = new SqlConnection(connstr))
            {
                conn.Open();
                using (SqlTransaction tx = conn.BeginTransaction())
                {
                    try
                    {
                        //using是保证资源一定会被回收的，离开using范围后自动调用Dispose方法（无论是否有异常）

                        //using==try...finally...

                        //using不会进行异常的catch

                        using (SqlCommand cmd1 = conn.CreateCommand())

                        using (SqlCommand cmd2 = conn.CreateCommand())
                        {
                            cmd1.Transaction = tx;//在SQLServer中必须把BeginTransaction返回的对象赋值给SqlCommand的
                            //Transaction属性。MySql也推荐折磨写不写也可以。
                            cmd1.CommandText = "insert into T_Persons(Name,Age) values('a',1)";
                            cmd1.ExecuteNonQuery();
                            cmd2.Transaction = tx;
                            cmd2.CommandText = "insert into T_Persons(Name,Age) values('b',2)";
                            cmd2.ExecuteNonQuery();
                        }

                        tx.Commit();
                    }
                    catch (Exception ex)
                    {
                        tx.Rollback();
                    }
                }
            }