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Python微信订餐小程序课程视频
https://blog.csdn.net/m0_56069948/article/details/122285951
Python实战量化交易理财系统
https://blog.csdn.net/m0_56069948/article/details/122285941
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 3.1
SDK
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:\dmdbms\drivers\dotNet
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;
///
/// 初始化DMClient的一个新实例
///
///
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
///
/// SQL查询语句
///
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;
}
///
/// 执行一条SQL语句，确定记录是否存在
///
/// SQL查询语句
///
public async Task<bool> ExistsAsync(string sql)
{
object obj = await GetSingleAsync(sql);
int cmdresult;
if (Equals(obj, null) || Equals(obj, DBNull.Value))
{
cmdresult = 0;
}
else
{
cmdresult = int.Parse(obj.ToString());
}
return cmdresult > 0;
}
///
/// 执行一条SQL语句，确定记录是否存在
///
/// SQL查询语句
/// SQL参数数组
///
public bool Exists(string sql, params DmParameter[] paras)
{
object obj = GetSingle(sql, paras);
int cmdresult;
if ((object.Equals(obj, null)) || (object.Equals(obj, DBNull.Value)))
{
cmdresult = 0;
}
else
{
cmdresult = int.Parse(obj.ToString());
}
return cmdresult > 0;
}
///
/// 执行一条SQL语句，确定记录是否存在
///
/// SQL查询语句
/// SQL参数数组
///
public async Task<bool> ExistsAsync(string sql, params DmParameter[] paras)
{
object obj = await GetSingleAsync(sql, paras);
int cmdresult;
if ((object.Equals(obj, null)) || (object.Equals(obj, DBNull.Value)))
{
cmdresult = 0;
}
else
{
cmdresult = int.Parse(obj.ToString());
}
return cmdresult > 0;
}
///
/// 获取记录条数
///
/// 表名
/// 查询条件
///
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);
}
else
{
return 0;
}
}
///
/// 获取记录条数
///
/// 表名
/// 查询条件
///
public async Task<int> GetCountAsync(string tableName, string sqlCondition)
{
string sql = "select count(1) from `" + tableName + "`";
if (!string.IsNullOrWhiteSpace(sqlCondition))
{
sql += " where " + sqlCondition;
}
object result = await GetSingleAsync(sql);
if (result != null)
{
return Convert.ToInt32(result);
}
else
{
return 0;
}
}
///
/// 获取记录条数
///
/// 表名
/// 查询条件
/// SQL参数数组
///
public int GetCount(string tableName, string sqlCondition, DmParameter[] paras)
{
string sql = "select count(1) from `" + tableName + "`";
if (!string.IsNullOrWhiteSpace(sqlCondition))
{
sql += " where " + sqlCondition;
}
object result = GetSingle(sql, paras);
if (result != null)
{
return Convert.ToInt32(result);
}
else
{
return 0;
}
}
///
/// 获取记录条数
///
/// 表名
/// 查询条件
/// SQL参数数组
///
public async Task<int> GetCountAsync(string tableName, string sqlCondition, DmParameter[] paras)
{
string sql = "select count(1) from `" + tableName + "`";
if (!string.IsNullOrWhiteSpace(sqlCondition))
{
sql += " where " + sqlCondition;
}
object result = await GetSingleAsync(sql, paras);
if (result != null)
{
return Convert.ToInt32(result);
}
else
{
return 0;
}
}
#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
///
/// SQL语句
/// 影响的记录数
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;
}
}
}
///
/// 执行SQL语句，返回影响的记录数
///
/// SQL语句
/// 影响的记录数
public async Task<int> ExecuteSqlAsync(string sql)
{
using (DmConnection connection = new DmConnection(connectionString))
{
using (DmCommand cmd = new DmCommand(sql, connection))
{
await connection.OpenAsync();
int rows = await cmd.ExecuteNonQueryAsync();
return rows;
}
}
}
///
/// 执行SQL语句，返回影响的记录数（可自定义超时时间）
///
/// SQL语句
/// 执行超时时间
/// 影响的记录数
public int ExecuteSqlByTime(string sql, int timeout)
{
using (DmConnection connection = new DmConnection(this.connectionString))
{
using (DmCommand cmd = new DmCommand(sql, connection))
{
connection.Open();
cmd.CommandTimeout = timeout;
int rows = cmd.ExecuteNonQuery();
return rows;
}
}
}
///
/// 执行SQL语句，返回影响的记录数（可自定义超时时间）
///
/// SQL语句
/// 执行超时时间
/// 影响的记录数
public async Task<int> ExecuteSqlByTimeAsync(string sql, int timeout)
{
using (DmConnection connection = new DmConnection(this.connectionString))
{
using (DmCommand cmd = new DmCommand(sql, connection))
{
await connection.OpenAsync();
cmd.CommandTimeout = timeout;
int rows = await cmd.ExecuteNonQueryAsync();
return rows;
}
}
}
///
/// 执行多条SQL语句，实现数据库事务。
///
/// 多条SQL语句
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;
}
}
}
}
}
///
/// 执行多条SQL语句，实现数据库事务。
///
/// 多条SQL语句
public async Task ExecuteSqlTransAsync(ArrayList sqlList)
{
using (DmConnection conn = new DmConnection(connectionString))
{
await conn.OpenAsync();
using (DbTransaction trans = await conn.BeginTransactionAsync())
{
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;
await cmd.ExecuteNonQueryAsync();
}
}
trans.Commit();
}
catch (DmException ex)
{
trans.Rollback();
throw ex;
}
}
}
}
}
///
/// 执行一条SQL查询语句，返回查询结果。
///
/// SQL查询语句
/// 查询结果
public object GetSingle(string sql)
{
using (DmConnection connection = new DmConnection(connectionString))
{
using (DmCommand cmd = new DmCommand(sql, connection))
{
connection.Open();
object obj = cmd.ExecuteScalar();
if ((object.Equals(obj, null)) || (object.Equals(obj, DBNull.Value)))
{
return null;
}
else
{
return obj;
}
}
}
}
///
/// 执行一条SQL查询语句，返回查询结果。
///
/// SQL查询语句
/// 查询结果
public async Task<object> GetSingleAsync(string sql)
{
using (DmConnection connection = new DmConnection(connectionString))
{
using (DmCommand cmd = new DmCommand(sql, connection))
{
await connection.OpenAsync();
object obj = await cmd.ExecuteScalarAsync();
if ((object.Equals(obj, null)) || (object.Equals(obj, DBNull.Value)))
{
return null;
}
else
{
return obj;
}
}
}
}
///
/// 执行查询语句，返回DbDataReader（切记要手工关闭DbDataReader）
///
/// 查询语句
/// DmDataReader
public DbDataReader ExecuteReader(string sql)
{
DmConnection connection = new DmConnection(connectionString);
DmCommand cmd = new DmCommand(sql, connection);
connection.Open();
return cmd.ExecuteReader();
}
///
/// 执行查询语句，返回DbDataReader（切记要手工关闭DbDataReader）
///
/// 查询语句
/// DmDataReader
public async Task ExecuteReaderAsync(string sql)
{
DmConnection connection = new DmConnection(connectionString);
DmCommand cmd = new DmCommand(sql, connection);
await connection.OpenAsync();
return await cmd.ExecuteReaderAsync();
}
///
/// 执行查询语句，返回DataSet
///
/// 查询语句
/// DataSet
public DataSet Query(string sql)
{
using (DmConnection connection = new DmConnection(connectionString))
{
using (DmDataAdapter command = new DmDataAdapter(sql, connection))
{
DataSet ds = new DataSet();
connection.Open();
command.Fill(ds, "ds");
return ds;
}
}
}
///
/// 执行查询语句，返回DataSet（可自定义超时时间）
///
///
///
///
public DataSet Query(string sql, int timeout)
{
using (DmConnection connection = new DmConnection(connectionString))
{
using (DmDataAdapter command = new DmDataAdapter(sql, connection))
{
DataSet ds = new DataSet();
connection.Open();
command.SelectCommand.CommandTimeout = timeout;
command.Fill(ds, "ds");
return ds;
}
}
}
#endregion 执行简单SQL语句
#region 执行带参数的SQL语句
///
/// 执行SQL语句，返回影响的记录数
///
/// SQL语句
/// SQL参数数组
/// 影响的记录数
public int ExecuteSql(string sql, params DmParameter[] paras)
{
using (DmConnection connection = new DmConnection(connectionString))
{
using (DmCommand cmd = new DmCommand())
{
PrepareCommand(cmd, connection, null, sql, paras);
int rows = cmd.ExecuteNonQuery();
cmd.Parameters.Clear();
return rows;
}
}
}
///
/// 执行SQL语句，返回影响的记录数
///
/// SQL语句
/// SQL参数数组
/// 影响的记录数
public async Task<int> ExecuteSqlAsync(string sql, params DmParameter[] paras)
{
using (DmConnection connection = new DmConnection(connectionString))
{
using (DmCommand cmd = new DmCommand())
{
await PrepareCommandAsync(cmd, connection, null, sql, paras);
int rows = await cmd.ExecuteNonQueryAsync();
cmd.Parameters.Clear();
return rows;
}
}
}
///
/// 执行添加SQL语句，返回记录的ID（自动产生的自增主键）
///
/// SQL语句
/// SQL参数
/// 记录的ID
public int ExecuteAdd(string sql, params DmParameter[] parms)
{
sql = sql + ";Select @@IDENTITY";
using (DmConnection connection = new DmConnection(connectionString))
{
using (DmCommand cmd = new DmCommand())
{
PrepareCommand(cmd, connection, null, sql, parms);
int recordID = Int32.Parse(cmd.ExecuteScalar().ToString());
cmd.Parameters.Clear();
return recordID;
}
}
}
///
/// 执行添加SQL语句，返回记录的ID（自动产生的自增主键）
///
/// SQL语句
/// SQL参数
/// 记录的ID
public async Task<int> ExecuteAddAsync(string sql, params DmParameter[] parms)
{
sql = sql + ";select @@identity as newautoid";
using (DmConnection connection = new DmConnection(connectionString))
{
using (DmCommand cmd = new DmCommand())
{
await PrepareCommandAsync(cmd, connection, null, sql, parms);
int recordID;
try
{
recordID = int.Parse((await cmd.ExecuteScalarAsync()).ToString());
}
catch
{
recordID = -1;
}
cmd.Parameters.Clear();
return recordID;
}
}
}
///
/// 执行多条SQL语句，实现数据库事务。
///
/// SQL语句的哈希表（key为sql语句，value是该语句的DmParameter[]）
public void ExecuteSqlTrans(Hashtable sqlList)
{
using (DmConnection conn = new DmConnection(connectionString))
{
conn.Open();
using (DbTransaction trans = conn.BeginTransaction())
{
using (DmCommand cmd = new DmCommand())
{
try
{
foreach (DictionaryEntry entry in sqlList)
{
var sql = entry.Key.ToString();
var paras = (DmParameter[])entry.Value;
PrepareCommand(cmd, conn, trans, sql, paras);
int val = cmd.ExecuteNonQuery();
cmd.Parameters.Clear();
}
trans.Commit();
}
catch (DmException ex)
{
trans.Rollback();
throw ex;
}
}
}
}
}
///
/// 执行多条SQL语句，实现数据库事务。
///
/// SQL语句的哈希表（key为sql语句，value是该语句的DmParameter[]）
public async Task ExecuteSqlTransAsync(Hashtable sqlList)
{
using (DmConnection conn = new DmConnection(connectionString))
{
await conn.OpenAsync();
using (DbTransaction trans = conn.BeginTransaction())
{
using (DmCommand cmd = new DmCommand())
{
try
{
foreach (DictionaryEntry entry in sqlList)
{
var sql = entry.Key.ToString();
var paras = (DmParameter[])entry.Value;
await PrepareCommandAsync(cmd, conn, trans, sql, paras);
int val = await cmd.ExecuteNonQueryAsync();
cmd.Parameters.Clear();
}
trans.Commit();
}
catch (DmException ex)
{
trans.Rollback();
throw ex;
}
}
}
}
}
///
/// 执行一条计算查询结果语句，返回查询结果。
///
/// SQL语句
/// SQL参数
/// 查询结果
public object GetSingle(string sql, params DmParameter[] parms)
{
using (DmConnection conn = new DmConnection(connectionString))
{
using (DmCommand cmd = new DmCommand())
{
PrepareCommand(cmd, conn, null, sql, parms);
object obj = cmd.ExecuteScalar();
cmd.Parameters.Clear();
if ((object.Equals(obj, null)) || (object.Equals(obj, DBNull.Value)))
{
return null;
}
else
{
return obj;
}
}
}
}
///
/// 执行一条计算查询结果语句，返回查询结果。
///
/// SQL语句
/// SQL参数
/// 查询结果
public async Task<object> GetSingleAsync(string sql, params DmParameter[] parms)
{
using (DmConnection conn = new DmConnection(connectionString))
{
using (DmCommand cmd = new DmCommand())
{
await PrepareCommandAsync(cmd, conn, null, sql, parms);
object obj = await cmd.ExecuteScalarAsync();
cmd.Parameters.Clear();
if ((object.Equals(obj, null)) || (object.Equals(obj, DBNull.Value)))
{
return null;
}
else
{
return obj;
}
}
}
}
///
/// 执行查询语句，返回DmDataReader (切记要手工关闭DmDataReader)
///
/// 查询语句
/// SQL参数
/// DmDataReader
public DbDataReader ExecuteReader(string sql, params DmParameter[] parms)
{
DmConnection connection = new DmConnection(connectionString);
DmCommand cmd = new DmCommand();
PrepareCommand(cmd, connection, null, sql, parms);
DbDataReader myReader = cmd.ExecuteReader();
cmd.Parameters.Clear();
return myReader;
}
///
/// 执行查询语句，返回DmDataReader (切记要手工关闭DmDataReader)
///
/// 查询语句
/// SQL参数
/// DmDataReader
public async Task ExecuteReaderAsync(string sql, params DmParameter[] parms)
{
DmConnection connection = new DmConnection(connectionString);
DmCommand cmd = new DmCommand();
await PrepareCommandAsync(cmd, connection, null, sql, parms);
var myReader = await cmd.ExecuteReaderAsync();
cmd.Parameters.Clear();
return myReader;
}
///
/// 执行查询语句，返回DataSet
///
/// 查询语句
/// 参数数组
/// DataSet
public DataSet Query(string sql, params DmParameter[] paras)
{
using (DmConnection connection = new DmConnection(connectionString))
{
using (DmCommand cmd = new DmCommand())
{
PrepareCommand(cmd, connection, null, sql, paras);
DataSet ds = new DataSet();
using (DmDataAdapter da = new DmDataAdapter(cmd))
{
da.Fill(ds, "ds");
cmd.Parameters.Clear();
return ds;
}
}
}
}
///
/// 准备SQL查询命令
///
/// SQL命令对象
/// SQL连接对象
/// SQL事务对象
/// SQL语句
/// SQL参数数组
private void PrepareCommand(DmCommand cmd, DmConnection conn, DbTransaction trans, string cmdText, DmParameter[] paras)
{
if (conn.State != ConnectionState.Open)
{
conn.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);
}
}
}
///
/// 准备SQL查询命令
///
/// SQL命令对象
/// SQL连接对象
/// SQL事务对象
/// SQL语句
/// SQL参数数组
private async Task PrepareCommandAsync(DmCommand cmd, DmConnection conn, DbTransaction trans, string cmdText, DmParameter[] paras)
{
if (conn.State != ConnectionState.Open)
{
await conn.OpenAsync();
}
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);
}
}
}
#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";
DmParameter[] paras = new DmParameter[] {
new DmParameter(":Id",model.Id),
new DmParameter(":City",model.City)
};
return _client.ExecuteSql(sql, paras) > 0 ? true : false;
}
public bool Delete(int id)
{
string sql = "delete from Person where Id=:Id";
DmParameter[] paras = new DmParameter[] {
new DmParameter(":Id",id),
};
return _client.ExecuteSql(sql, paras) > 0 ? true : false;
}
public PersonModel Get(int id)
{
string sql = "select Id,Name,City from Person where Id=:Id";
DmParameter[] paras = new DmParameter[] {
new DmParameter(":Id",id),
};
PersonModel model = null;
using (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 GetList()
{
var list = new List();
using (var reader = (DmDataReader)\_client.ExecuteReader("select Id,Name,City from Person"))
{
while (reader.Read())
{
var model = new PersonModel();
model.Id = reader.GetInt32(0);
model.Name = reader.GetString(1);
model.City = reader.GetString(2);
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(sql, new { Id = id });
}
public List GetList()
{
string sql = "select Id,Name,City from Person";
return DmConnectionFactory.GetConn().Query(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。
好了，以上就是本文的主要内容。如有错漏欢迎指正。
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