ado.net快速上手实践篇（一）

文章来源：IT工程信息网 http://www.systhinker.com/?viewnews-11675
前言：这两天重温经典，对ado.net的东西稍微深入的了解了一下，顺便写点代码练练手，全当是复习笔记吧。
一、简单说说ado.net的5大常用对象

既然说ado.net，当然不能免俗地要提到5大常用对象。本文不会对ado.net的5大对象和它们的关系进行过多阐释，不过我们应该对下面这张图的结构有个了解：



关于上图图示中的5大对象，经常做以数据为驱动的mis系统的童鞋应该不会陌生。本文一笔带过。下面我们一步一步实现以ado.net为核心的数据访问程序。

【注意：下面的示例代码和demo是楼猪本周六和周日两天时间实现的，未经详细测试，可能有重大bug，下载学习使用的童鞋务必注意】

二、数据访问持久化层
1、IDbOperation接口




代码

using System.Collections.Generic;
using System.Data;
using System.Data.Common;

namespace AdoNetDataAccess.Core.Contract
{
public interface IDbOperation
{
DbCommand CreateDbCommd(DbConnection sqlConn, DbTransaction transaction, string sqlStr, CommandType cmdType, List<DbParameter> listParams);

DbParameter CreateDbPrameter(string paramName, object paramValue);

DbDataReader ExecuteReader(string sqlStr, CommandType cmdType, List<DbParameter> listParams);

DataTable FillDataTable(string sqlStr, CommandType cmdType, List<DbParameter> listParams);

DataSet FillDataSet(string sqlStr, CommandType cmdType, List<DbParameter> listParams);

object ExecuteScalar(string sqlStr, CommandType cmdType, List<DbParameter> listParams);

int ExecuteNonQuery(string sqlStr, CommandType cmdType, List<DbParameter> listParams);

/// <summary>
/// 批量插入
/// </summary>
/// <param name="tableName">表名称</param>
/// <param name="dt">组装好的要批量导入的datatable</param>
/// <returns></returns>
bool ExecuteBatchInsert(string tableName, int batchSize, int copyTimeout, DataTable dt);

void OpenConnection();

void CloseConnection();
}
}

上面的接口包括增删改查，批量插入以及数据库连接对象的连接和关闭等常用操作，您可以根据命名和参数轻松理解函数的含义。根据楼猪的开发经验，对于平时的数据库操作，上述方法差不多够用了。当然您也可以按照自己需要，重写组织添加其他函数。
2、针对一种数据源的数据操作实现
底层的数据操作接口定义好后，就要针对一种数据源，具体实现上述的数据操作。这里楼猪选择了Sql Server。我们也可以实现其他数据源的数据访问操作，按照配置，利用抽象工厂动态反射选择是哪一种数据源的实现。这里按下不表，有心的童鞋自己可以动手一试。下面是具体的实现：




代码

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Data.SqlClient;
using System.Transactions;

namespace AdoNetDataAccess.Core.Implement
{
using AdoNetDataAccess.Core.Contract;

public class SqlServer : IDbOperation, IDisposable
{
private int cmdTimeOut = 60;
private DbConnection sqlConn = null;
private DbCommand cmd = null;

private SqlServer()
{

}

public SqlServer(string sqlConStr)
{
sqlConn = new SqlConnection(sqlConStr);
cmdTimeOut = sqlConn.ConnectionTimeout;
}

public SqlServer(string sqlConStr, int timeOut)
{
sqlConn = new SqlConnection(sqlConStr);
if (timeOut < 0)
{
timeOut = sqlConn.ConnectionTimeout;
}
cmdTimeOut = timeOut;
}

#region contract method

public DbCommand CreateDbCommd(DbConnection sqlConn, DbTransaction transaction, string sqlStr, CommandType cmdType, List<DbParameter> listParams)
{
DbCommand cmd = new SqlCommand();
cmd.Connection = sqlConn;
cmd.CommandText = sqlStr;
cmd.CommandType = cmdType;
if (transaction != null)
{
cmd.Transaction = transaction;
}
if (listParams != null && listParams.Count > 0)
{
cmd.Parameters.AddRange(listParams.ToArray());
}
cmd.CommandTimeout = cmdTimeOut;
OpenConnection();
return cmd;
}

public DbParameter CreateDbPrameter(string paramName, object paramValue)
{
SqlParameter sp = new SqlParameter(paramName, paramValue);
return sp;
}

public DbDataReader ExecuteReader(string sqlStr, CommandType cmdType, List<DbParameter> listParams)
{
DbDataReader rdr = null;
try
{
OpenConnection();
cmd = CreateDbCommd(sqlConn, null, sqlStr, cmdType, listParams);
rdr = cmd.ExecuteReader();
}
catch (Exception ex)
{
throw ex;
}
return rdr;
}

public DataTable FillDataTable(string sqlStr, CommandType cmdType, List<DbParameter> listParams)
{
OpenConnection();
DbTransaction trans = sqlConn.BeginTransaction();
DbCommand cmd = CreateDbCommd(sqlConn, trans, sqlStr, cmdType, listParams);
SqlDataAdapter sqlDataAdpter = new SqlDataAdapter(cmd as SqlCommand);
DataTable dt = new DataTable();
try
{
sqlDataAdpter.Fill(dt);
trans.Commit();
}
catch (Exception e)
{
trans.Rollback();
throw new Exception("执行数据库操作失败, sql: " + sqlStr, e);
}
finally
{
sqlDataAdpter.Dispose();
cmd.Dispose();
trans.Dispose();
CloseConnection();
}
return dt;
}

public DataSet FillDataSet(string sqlStr, CommandType cmdType, List<DbParameter> listParams)
{
OpenConnection();
DbTransaction trans = sqlConn.BeginTransaction();
DbCommand cmd = CreateDbCommd(sqlConn, trans, sqlStr, cmdType, listParams);
SqlDataAdapter sqlDataAdpter = new SqlDataAdapter(cmd as SqlCommand);
DataSet ds = new DataSet();
try
{
sqlDataAdpter.Fill(ds);
trans.Commit();
}
catch (Exception e)
{
trans.Rollback();
throw new Exception("执行数据库操作失败, sql: " + sqlStr, e);
}
finally
{
sqlDataAdpter.Dispose();
cmd.Dispose();
trans.Dispose();
CloseConnection();
}
return ds;
}

public object ExecuteScalar(string sqlStr, CommandType cmdType, List<DbParameter> listParams)
{
object result = null;
OpenConnection();
DbTransaction trans = sqlConn.BeginTransaction();
try
{
cmd = CreateDbCommd(sqlConn, trans, sqlStr, cmdType, listParams);
result = cmd.ExecuteScalar();
trans.Commit();
}
catch (Exception e)
{
trans.Rollback();
throw new Exception("执行数据库操作失败, sql: " + sqlStr, e);
}
finally
{
trans.Dispose();
CloseConnection();
}
return result;
}

public int ExecuteNonQuery(string sqlStr, CommandType cmdType, List<DbParameter> listParams)
{
int result = -1;
OpenConnection();
DbTransaction trans = sqlConn.BeginTransaction();
try
{
cmd = CreateDbCommd(sqlConn, trans, sqlStr, cmdType, listParams);
result = cmd.ExecuteNonQuery();
trans.Commit();
}
catch (Exception e)
{
trans.Rollback();
throw new Exception("执行数据库操作失败, sql: " + sqlStr, e);
}
finally
{
trans.Dispose();
CloseConnection();
}
return result;
}

/// <summary>
/// 批量插入
/// </summary>
/// <param name="tableName"></param>
/// <param name="batchSize"></param>
/// <param name="copyTimeout"></param>
/// <param name="dt"></param>
/// <returns></returns>
public bool ExecuteBatchInsert(string tableName, int batchSize, int copyTimeout, DataTable dt)
{
bool flag = false;
try
{
using (TransactionScope scope = new TransactionScope())
{
OpenConnection();
using (SqlBulkCopy sbc = new SqlBulkCopy(sqlConn as SqlConnection))
{
//服务器上目标表的名称
sbc.DestinationTableName = tableName;
sbc.BatchSize = batchSize;
sbc.BulkCopyTimeout = copyTimeout;
for (int i = 0; i < dt.Columns.Count; i++)
{
//列映射定义数据源中的列和目标表中的列之间的关系
sbc.ColumnMappings.Add(dt.Columns[i].ColumnName, dt.Columns[i].ColumnName);
}
sbc.WriteToServer(dt);
flag = true;
scope.Complete();//有效的事务
}
}
}
catch (Exception ex)
{
throw ex;
}
return flag;
}

public void OpenConnection()
{
if (sqlConn.State == ConnectionState.Broken || sqlConn.State == ConnectionState.Closed)
sqlConn.Open();
}

public void CloseConnection()
{
sqlConn.Close();
}

#endregion

#region dispose method

/// <summary>
/// dispose接口方法
/// </summary>
public void Dispose()
{

}

#endregion
}
}

到这里，我们实现了SqlServer类里的方法，对Ms SqlServer数据库我们就已经可以进行简单的基础的CRUD操作了。

三、简单直观的对象实体转换
在第二步中，我们已经实现了简单的数据CRUD操作。根据楼猪使用ORM的经验和习惯，我们也应该对一些查询结果进行转换，因为以类的组织方式比直接呈现ado.net对象更容易让人接受，效率高低反在其次。下面利用常见的反射原理，简单实现一个对象实体转换器ModelConverter类：




代码

using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Reflection;
using System.Threading;

namespace AdoNetDataAccess.Core.Obj2Model
{
using AdoNetDataAccess.Core.Contract;

public sealed class ModelConverter
{
private static readonly object objSync = new object();

#region query for list

/// <summary>
/// 查询数据表项并转换为对应实体
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="objType"></param>
/// <param name="rdr"></param>
/// <returns></returns>
public static IList<T> QueryForList<T>(string sqlStr, CommandType cmdType, List<DbParameter> listParams, Type objType, IDbOperation dbOperation)
where T : class, new()
{
IDataReader rdr = dbOperation.ExecuteReader(sqlStr, cmdType, listParams);
IList<T> listModels = new List<T>();
try
{
Monitor.Enter(objSync);
Hashtable ht = CreateHashColumnName(rdr);
while (rdr.Read())
{
Object obj = Activator.CreateInstance(objType);
PropertyInfo[] properties = objType.GetProperties();
foreach (PropertyInfo propInfo in properties)
{
string columnName = propInfo.Name.ToUpper();
if (ht.ContainsKey(columnName) == false)
{
continue;
}
int index = rdr.GetOrdinal(propInfo.Name);
object columnValue = rdr.GetValue(index);
if (columnValue != System.DBNull.Value)
{
SetValue(propInfo, obj, columnValue);
}
}
T model = default(T);
model = obj as T;
listModels.Add(model);
}
}
finally
{
rdr.Close();
rdr.Dispose();
Monitor.Exit(objSync);
}
return listModels;
}

#endregion

#region query for dictionary

/// <summary>
/// 查询数据表项并转换为对应实体
/// </summary>
/// <typeparam name="K"></typeparam>
/// <typeparam name="T"></typeparam>
/// <param name="key">字典对应key列名</param>
/// <param name="objType"></param>
/// <param name="rdr"></param>
/// <returns></returns>
public

文章来源：IT工程信息网 http://www.systhinker.com/?viewnews-11675