目录
背景环境SDK操作数据库DbHelperSQL方式Dapper方式背景
某个项目需要实现基础软件全部国产化，其中操作系统指定银河麒麟，数据库使用达梦V8，CPU平台的范围包括x64、龙芯、飞腾、鲲鹏等。考虑到这些基础产品对.NET的支持，最终选择了.NET Core 3.1。
环境
CPU平台：x86-64 / Arm64操作系统：银河麒麟 v4数据库：DM8.NET：.NET Core 3.1SDK
达梦自己提供了.NET操作其数据库的SDK，可以通过NuGet安装，也可以通过安装达梦数据库获取。因为NuGet上的版本不知道是谁提供的，所以这里以安装数据库获取相关SDK为例。
在官网下载DM8的数据库安装文件：https://www.dameng.com/list_103.html
下载前需要先登录，随便注册一个帐号就好了。
这里需要选择CPU和操作系统，按照你的开发环境选择即可，下载后按照提示安装。
这里以Windows10为例，安装后SDK文件的位置在：C:dmdbmsdriversdotNet
这里边有EF的SDK，也有NHibernate的SDK，不过这篇文章只使用最基础的基于ADO.NET的SDK。
这些SDK在文件夹DmProvider下边，这里还提供了一个Nuget包，可以放到自己的Nuget仓库中，方便内部安装。
可以看到，这个SDK可以支持.NET Core2.0以上的所有.NET版本。
操作数据库
这里提供两种方式：传统的DbHelperSQL方式 和 Dapper 方式。
DbHelperSQL方式
这种方式早年用的比较多，现在还有很多项目在使用，通过定义一组工具方法包装对数据库的各种增删改查操作。下面给出代码：
public class DmDbClient { private string connectionString = string.Empty; /// <summary> /// 初始化DMClient的一个新实例 /// </summary> /// <param name="str"></param> public DmDbClient(string str) { connectionString = str; } #region 通用快捷方法 /// 执行一条SQL语句，确定记录是否存在 /// <param name="sql">SQL查询语句</param> /// <returns></returns> public bool Exists(string sql) object obj = GetSingle(sql); int cmdresult; if (Equals(obj, null) || Equals(obj, DBNull.Value)) { cmdresult = 0; } else cmdresult = int.Parse(obj.ToString()); return cmdresult > 0; public async Task<bool> ExistsAsync(string sql) object obj = await GetSingleAsync(sql); /// <param name="paras">SQL参数数组</param> public bool Exists(string sql, params DmParameter[] paras) object obj = GetSingle(sql, paras); if ((object.Equals(obj, null)) || (object.Equals(obj, DBNull.Value))) public async Task<bool> ExistsAsync(string sql, params DmParameter[] paras) object obj = await GetSingleAsync(sql, paras); /// 获取记录条数 /// <param name="tableName">表名</param> /// <param name="sqlCondition">查询条件</param> public int GetCount(string tableName, string sqlCondition) string sql = "select count(1) from `" + tableName + "`"; if (!string.IsNullOrWhiteSpace(sqlCondition)) sql += " where " + sqlCondition; object result = GetSingle(sql); if (result != null) return Convert.ToInt32(result); return 0; public async Task<int> GetCountAsync(string tableName, string sqlCondition) object result = await GetSingleAsync(sql); public int GetCount(string tableName, string sqlCondition, DmParameter[] paras) object result = GetSingle(sql, paras); public async Task<int> GetCountAsync(string tableName, string sqlCondition, DmParameter[] paras) object result = await GetSingleAsync(sql, paras); #endregion 通用快捷方法 #region 执行简单SQL语句 /// 执行SQL语句，返回影响的记录数 /// <param name="sql">SQL语句</param> /// <returns>影响的记录数</returns> public int ExecuteSql(string sql) using (DmConnection connection = new DmConnection(connectionString)) using (DmCommand cmd = new DmCommand(sql, connection)) { connection.Open(); int rows = cmd.ExecuteNonQuery(); return rows; } public async Task<int> ExecuteSqlAsync(string sql) await connection.OpenAsync(); int rows = await cmd.ExecuteNonQueryAsync(); /// 执行SQL语句，返回影响的记录数（可自定义超时时间） /// <param name="timeout">执行超时时间</param> public int ExecuteSqlByTime(string sql, int timeout) using (DmConnection connection = new DmConnection(this.connectionString)) cmd.CommandTimeout = timeout; public async Task<int> ExecuteSqlByTimeAsync(string sql, int timeout) /// 执行多条SQL语句，实现数据库事务。 /// <param name="sqlList">多条SQL语句</param> public void ExecuteSqlTrans(ArrayList sqlList) using (DmConnection conn = new DmConnection(connectionString)) conn.Open(); using (DbTransaction trans = conn.BeginTransaction()) using (DmCommand cmd = new DmCommand()) { cmd.Connection = conn; cmd.Transaction = trans; try { for (int n = 0; n < sqlList.Count; n++) { string sql = sqlList[n].ToString(); if (sql.Trim().Length > 1) { cmd.CommandText = sql; cmd.ExecuteNonQuery(); } } trans.Commit(); } catch (DmException ex) trans.Rollback(); throw ex; } public async Task ExecuteSqlTransAsync(ArrayList sqlList) await conn.OpenAsync(); using (DbTransaction trans = await conn.BeginTransactionAsync()) await cmd.ExecuteNonQueryAsync(); /// 执行一条SQL查询语句，返回查询结果。 /// <returns>查询结果</returns> public object GetSingle(string sql) object obj = cmd.ExecuteScalar(); if ((object.Equals(obj, null)) || (object.Equals(obj, DBNull.Value))) return null; else return obj; public async Task<object> GetSingleAsync(string sql) object obj = await cmd.ExecuteScalarAsync(); /// 执行查询语句，返回DbDataReader（切记要手工关闭DbDataReader） /// <param name="sql">查询语句</param> /// <returns>DmDataReader</returns> public DbDataReader ExecuteReader(string sql) DmConnection connection = new DmConnection(connectionString); DmCommand cmd = new DmCommand(sql, connection); connection.Open(); return cmd.ExecuteReader(); public async Task<DbDataReader> ExecuteReaderAsync(string sql) await connection.OpenAsync(); return await cmd.ExecuteReaderAsync(); /// 执行查询语句，返回DataSet /// <returns>DataSet</returns> public DataSet Query(string sql) using (DmDataAdapter command = new DmDataAdapter(sql, connection)) DataSet ds = new DataSet(); command.Fill(ds, "ds"); return ds; /// 执行查询语句，返回DataSet（可自定义超时时间） /// <param name="sql"></param> /// <param name="timeout"></param> public DataSet Query(string sql, int timeout) command.SelectCommand.CommandTimeout = timeout; #endregion 执行简单SQL语句 #region 执行带参数的SQL语句 public int ExecuteSql(string sql, params DmParameter[] paras) using (DmCommand cmd = new DmCommand()) PrepareCommand(cmd, connection, null, sql, paras); cmd.Parameters.Clear(); public async Task<int> ExecuteSqlAsync(string sql, params DmParameter[] paras) await PrepareCommandAsync(cmd, connection, null, sql, paras); /// 执行添加SQL语句，返回记录的ID（自动产生的自增主键） /// <param name="parms">SQL参数</param> /// <returns>记录的ID</returns> public int ExecuteAdd(string sql, params DmParameter[] parms) sql = sql + ";Select @@IDENTITY"; PrepareCommand(cmd, connection, null, sql, parms); int recordID = Int32.Parse(cmd.ExecuteScalar().ToString()); return recordID; public async Task<int> ExecuteAddAsync(string sql, params DmParameter[] parms) sql = sql + ";select @@identity as newautoid"; await PrepareCommandAsync(cmd, connection, null, sql, parms); int recordID; try recordID = int.Parse((await cmd.ExecuteScalarAsync()).ToString()); catch recordID = -1; /// <param name="sqlList">SQL语句的哈希表（key为sql语句，value是该语句的DmParameter[]）</param> public void ExecuteSq int val = cmd.ExecuteNonQuery(); cmd.Parameters.Clear(); public async Task ExecuteSqlTransAsync(Hashtable sqlList) await PrepareCommandAsync(cmd, conn, trans, sql, paras); int val = await cmd.ExecuteNonQueryAsync(); /// 执行一条计算查询结果语句，返回查询结果。 public object GetSingle(string sql, params DmParameter[] parms) PrepareCommand(cmd, conn, null, sql, parms); public async Task<object> GetSingleAsync(string sql, params DmParameter[] parms) await PrepareCommandAsync(cmd, conn, null, sql, parms); /// 执行查询语句，返回DmDataReader (切记要手工关闭DmDataReader) public DbDataReader ExecuteReader(string sql, params DmParameter[] parms) DmCommand cmd = new DmCommand(); PrepareCommand(cmd, connection, null, sql, parms); DbDataReader myReader = cmd.ExecuteReader(); cmd.Parameters.Clear(); return myReader; public async Task<DbDataReader> ExecuteReaderAsync(string sql, params DmParameter[] parms) await PrepareCommandAsync(cmd, connection, null, sql, parms); var myReader = await cmd.ExecuteReaderAsync(); /// <param name="paras">参数数组</param> public DataSet Query(string sql, params DmParameter[] paras) using (DmDataAdapter da = new DmDataAdapter(cmd)) da.Fill(ds, "ds"); cmd.Parameters.Clear(); retWHhEafmurn ds; /// 准备SQL查询命令 /// <param name="cmd">SQL命令对象</param> /// <param name="conn">SQL连接对象</param> /// <param name="trans">SQL事务对象</param> /// <param name="cmdText">SQL语句</param> private void PrepareCommand(DmCommand cmd, DmConnection conn, DbTransaction trans, string cmdText, DmParameter[] paras) if (conn.State != ConnectionState.Open) cmd.Connection = conn; cmd.CommandText = cmdText; if (trans != null) cmd.Transaction = trans; cmd.CommandType = CommandType.Text; if (paras != null) foreach (DmParameter parameter in paras) if ((parameter.Direction == ParameterDirection.InputOutput || parameter.Direction == ParameterDirection.Input) && (parameter.Value == null)) parameter.Value = DBNull.Value; cmd.Parameters.Add(parameter); private async Task PrepareCommandAsync(DmCommand cmd, DmConnection conn, DbTransaction trans, string cmdText, DmParameter[] paras) #endregion 执行带参数的SQL语句 }使用方法也很简单，传入SQL语句和参数即可。这里给出几个增删改查的例子：
public class PersonAdoNetDAL : IPersonDAL { static readonly DmDbClient _client = new DmDbClient("Server=127.0.0.1; UserId=TESTDB; PWD=1234567"); public int Add(PersonModel model) { string sql = "insert into Person(Name,City) Values(:Name,:City)"; DmParameter[] paras = new DmParameter[] { new DmParameter(":Name",model.Name), new DmParameter(":City",model.City) }; return _client.ExecuteAdd(sql, paras); } public bool Update(PersonModel model) string sql = "update Person set City=:City where Id=:Id"; new DmParameter(":Id",model.Id), return _client.ExecuteSql(sql, paras) > 0 ? true : false; public bool Delete(int id) string sql = "delete from Person where Id=:Id"; new DmParameter(":Id",id), public PersonModel Get(int id) string sql = "select Id,Name,City from Person where Id=:Id"; PersonModel model = null; usinwww.easck.comg (var reader = (DmDataReader)_client.ExecuteReader(sql, paras)) { while (reader.Read()) { model = new PersonModel(); model.Id = reader.GetInt32(0); model.Name = reader.GetString(1); model.City = reader.GetString(2); } } return model; public List<PersonModel> GetList() var list = new List<PersonModel>(); using (var reader = (DmDataReader)_client.ExecuteReader("select Id,Name,City from Person")) var model = new PersonModel(); list.Add(model); return list; }需要注意达梦数据库的参数是用冒号作为前缀的。另外数据表和字段的名字建议全部使用大写字母，单词之间使用下划线分隔，也就是蛇形命名法。此时SQL语句就不用关心大小写了，怎么写都行。
Dapper方式
Dapper是一个轻量级的ORM框架，现在使用的也很广泛，可以简化代码编写。因为Dapper扩展的IDbConnection，这是ADO.NET中的东西，我们使用的DmProvider也是实现了ADO.NET相关接口，所以Dapper可以通过DmProvider操作达梦数据库。
首先定义一个获取数据库连接对象的工厂类：
public class DmConnectionFactory { static string sqlConnString = "Server=127.0.0.1; UserId=TESTDB; PWD=123456"; public static IDbConnection GetConn() { return new DmConnection(sqlConnString); } }然后就可以使用它执行SQL语句了：
public class PersonDapperDAL : IPersonDAL { public PersonDapperDAL() { } public PersonModel Get(int id) { string sql = "select Id,Name,City from Person where Id=:Id"; return DmConnectionFactory.GetConn().QueryFirstOrDefault<PersonModel>(sql, new { Id = id }); } public List<PersonModel> GetList() { string sql = "select Id,Name,City from Person"; return DmConnectionFactory.GetConn().Query<PersonModel>(sql).ToList(); } public int Add(PersonModel model) { string sql = "insert into Person(Name,City) Values(:Name,:City);Select @@IDENTITY"; return DmConnectionFactory.GetConn().QuerySingle<int>(sql, model); } public bool Update(PersonModel model) { string sql = "update Person set City=:City where Id=:Id"; int result = DmConnectionFactory.GetConn().Execute(sql, model); return result > 0; } public bool Delete(int id) { string sql = "delete from Person where Id=:Id"; int result = DmConnectionFactory.GetConn().Execute(sql, new { Id = id }); return result > 0; } }Query、Execute这些方法都是Dapper定义的，可以看到能够少写很多代码。这里也不用打开连接、关闭连接，也不用写using，因为Dapper的这些方法中已经做了相关处理。
