.NetCore 3.1 Dapper

 public class Dapper
    {
        public string ConnectionString { get; set; }

        public Dapper()
        {
            var Configuration = new ConfigurationBuilder()
                .Add(new JsonConfigurationSource { Path = "appsettings.json", ReloadOnChange = true })
                .Build();

            ConnectionString = Configuration["ConnectionStrings:MySql"];
        }

        public async Task<bool> InsertAsync<T>(T t) where T : class
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                return await connection.InsertAsync(t) > 0;
            }
        }

        public async Task<bool> InsertAsync<T>(List<T> list) where T : class
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                return await connection.InsertAsync(list) > 0;
            }
        }

        public async Task<bool> DeleteAsync<T>(T t) where T : class
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                return await connection.DeleteAsync(t);
            }
        }

        public async Task<bool> UpdateAsync<T>(T t) where T : class
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                return await connection.UpdateAsync(t);
            }
        }

        public async Task<IEnumerable<T>> GetAllAsync<T>() where T : class
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                return await connection.GetAllAsync<T>();
            }
        }

        public async Task<T> GetByIDAsync<T>(int id) where T : class
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                return await connection.GetAsync<T>(id);
            }
        }

        public async Task<int> ExecuteAsync(string path)
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                using (StreamReader streamReader = new StreamReader(path, System.Text.Encoding.UTF8))
                {
                    var script = await streamReader.ReadToEndAsync();
                    return await connection.ExecuteAsync(script);
                }
            }
        }

        public async Task<int> ExecuteAsync(string sql, object param = null)
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                return await connection.ExecuteAsync(sql, param);
            }
        }

        public async Task<bool> ExecuteAsyncTransaction(List<string> list)
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                connection.Open();

                IDbTransaction transaction = connection.BeginTransaction();

                try
                {
                    foreach (var sql in list)
                    {
                        await connection.ExecuteAsync(sql, null, transaction);
                    }

                    transaction.Commit();

                    return true;
                }
                catch (Exception e)
                {
                    transaction.Rollback();

                    return false;
                }
            }
        }

        public async Task<bool> ExecuteAsyncTransaction(List<KeyValuePair<string, object>> list)
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                connection.Open();

                IDbTransaction transaction = connection.BeginTransaction();

                try
                {
                    foreach (var item in list)
                    {
                        await connection.ExecuteAsync(item.Key, item.Value, transaction);
                    }

                    transaction.Commit();

                    return true;
                }
                catch (Exception e)
                {
                    transaction.Rollback();

                    return false;
                }
            }
        }

        public async Task<IEnumerable<dynamic>> QueryAsync(string sql, object param = null)
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                return await connection.QueryAsync(sql, param);
            }
        }

        public async Task<dynamic> QueryFirstOrDefaultAsync(string sql, object param = null)
        {
            using (IDbConnection connection = new MySqlConnection(ConnectionString))
            {
                return await connection.QueryFirstOrDefaultAsync(sql, param);
            }
        }
    }

            Dapper dapper = new Dapper();

            Student student = new Student()
            {
                sid = 1,
                sname = "张三",
                sage = 20,
                ssex = "男"
            };

            List<Student> students = new List<Student>()
            {
                new Student(){sid = 1, sname = "张三", sage = 20,ssex = "男"},
                new Student(){sid = 2, sname = "李思思", sage = 23,ssex = "女"},
                new Student(){sid = 3, sname = "王五", sage = 27,ssex = "男"}
            };

            //增加
            await dapper.InsertAsync<Student>(student);
            await dapper.InsertAsync<Student>(students);

            //修改 / 删除 1、以[ExplicitKey] /[key]为条件
            await dapper.UpdateAsync(new Student() { sid = 1, sname = "修改", sage = 20, ssex = "男" });
            await dapper.DeleteAsync(new Student() { sid = 1 });

            //修改 / 删除 2、直接写sql，灵活、简单
            await dapper.ExecuteAsync(@"update student
                                           set sid=0
                                         where sname=@sname or sage=@sage;",
                                         new { sname = "李思思", sage = 27 });
            await dapper.ExecuteAsync(@"delete from student
                                         where sname=@sname or sage=@sage;",
                                         new { sname = "李思思", sage = 27 });

            //简单事务: 无参数
            List<string> list1 = new List<string>()
            {
                "insert into student(sid,sname) values(‘1‘,‘1‘)",
                "insert into teacher(tid,tname) values(‘1‘,‘1‘)"
            };
            await dapper.ExecuteAsyncTransaction(list1);

            //简单事务: 有参数
            List<KeyValuePair<string, object>> list2 = new List<KeyValuePair<string, object>>();
            list2.Add(new KeyValuePair<string, object>(
                "insert into student(sid,sname) values(@sid,@sname)",
                 new { sid = 22, sname = "test1" }));

            list2.Add(new KeyValuePair<string, object>(
                "insert into teacher(tid,tname) values(@tid,@tname)",
                new { tid = 33, tname = "test2" }));
            await dapper.ExecuteAsyncTransaction(list2);

            //查询
            var result1 = dapper.GetAllAsync<Student>();
            var result2 = dapper.GetByIDAsync<Student>(1);
            var result3 = dapper.QueryAsync(@"SELECT s.sid AS ‘学号‘, s.sname AS ‘姓名‘,
                                                     COUNT(sc.cid) AS ‘课程数目‘,
                                                     SUM(sc.score) AS ‘总分数‘
                                                FROM student s, sc sc
                                               WHERE s.sid = sc.sid
                                            GROUP BY s.sid, s.sname");