string constr = "";
            using (SqlConnection con = new SqlConnection(constr))
            {
                con.Open();
                using (SqlTransaction tran = con.BeginTransaction())
                {
                    using (SqlCommand cmd = new SqlCommand("sql", con))
                    {
                        cmd.Transaction = tran;
                        cmd.ExecuteNonQuery();
                        cmd.CommandText = "sql";
                        cmd.Parameters.Clear();
                        cmd.Parameters.AddRange(null);
                        cmd.ExecuteNonQuery();
                    }
                    //tran.Commit();无异常提交
                    tran.Rollback();//异常回滚
                }

            }