原文:黄聪：Microsoft Enterprise Library 5.0 系列教程(五) Data Access Application Block
企业库数据库访问模块通过抽象工厂模式,允许用户通过简单的配置选择不同的数据库作为程序的数据源,大大解决了切换数据库时带来的麻烦.因为我本机只安装了SQL Server 2005,所以在此只做SQL的演示,需要深究的朋友可以访问以下网站:
http://msdn.microsoft.com/en-us/library/ff664408%28v=PandP.50%29.aspx
企业库数据库访问模块的几大功能:
1. 最简单的功能,通过ExecuteNonQuery.方法执行SQL语句.
2. 执行ExecuteDataSet,返回DataSet类型的数据集.
3. 执行ExecuteScalar,获取返回的第一行第一列的信息.
4. 执行存储过程.
5. 通过代码实现事务.
6. 通过DataSet更新数据库.
7. 返回值XML化.
8. 将返回的数据对象化.
9. 异步访问数据库.
以上的功能我会在下面一一介绍,测试程序我已打包,大家可以点击这里下载.
下面介绍如何使用Microsoft Enterprise Library 5.0中的数据库访问模块.
1. 首先创建一个测试数据库,创建数据库的SQL文件我打包在压缩包里了,大家可以点击上面的下载链接下载.执行完SQL文件后,可以看到我们创建好的TestDB数据库:
2. 下载安装好MicrosoftEnterprise Library 5.0,然后在运行EntLibConfig.exe,选择Blocks菜单 ,单击 AddDatabase Settings .
3. 配置好文件之后保存为App.config文件,并添加到创建好的应用程序中.并添加相应的引用,在此我不再多讲,大家下载我打包好的程序运行即可看到
4. 下面来介绍我在应用程序中实现的各个功能:
(1) 通过ExecuteNonQuery.方法执行SQL语句:
///<summary>/// 执行ExecuteNonQuery///</summary>privatevoid ExecuteNonQuery_Click(object sender, EventArgs e){ db.ExecuteNonQuery(CommandType.Text, "INSERT INTO [College] ([CollegeID],[Name]) values (6,'体育学院')");}
(2) 执行ExecuteDataSet,返回DataSet类型的数据集.
///<summary>/// 执行ExecuteDataSet，返回College列表///</summary>///<returns></returns>privatevoid ExecuteDataSet_Click(object sender, EventArgs e){ string sql ="select * from College"; DbCommand dw = db.GetSqlStringCommand(sql); dataGridView1.DataSource = db.ExecuteDataSet(dw).Tables[];}
(3) 执行ExecuteScalar,返回第一行第一列的值.
///<summary>/// 执行ExecuteScalar,返回第一行第一列的值///</summary>///<returns></returns>privatevoid ExecuteScalar_Click(object sender, EventArgs e){ Database db = DatabaseFactory.CreateDatabase("ConnectionString"); string sql ="select [Name] from College where [CollegeID] = 1"; DbCommand dc = db.GetSqlStringCommand(sql); string str ="获取的学院名称为:"+ (string)db.ExecuteScalar(dc); MessageBox.Show(str); sql ="select [CollegeID] from College where [CollegeID] = 1"; dc = db.GetSqlStringCommand(sql); str ="获取的学院ID为:"+ (int)db.ExecuteScalar(dc); MessageBox.Show(str);}
(4) 执行存储过程.
///<summary>/// 执行存储过程///</summary>privatevoid StoredProcCommand_Click(object sender, EventArgs e){ DbCommand dc = db.GetStoredProcCommand("usp_College_LoadByID"); db.AddInParameter(dc, "@CollegeID", System.Data.DbType.Int32, ); dataGridView1.DataSource = db.ExecuteDataSet(dc).Tables[];}
(5) 通过代码实现事务.
///<summary>/// 事务///</summary>privatevoid Transaction_Click(object sender, EventArgs e){ DbCommand dc1 = db.GetStoredProcCommand("usp_College_Insert"); db.AddInParameter(dc1, "@CollegeID", DbType.Int32, ); db.AddInParameter(dc1, "@Name", DbType.String, "文旅学院"); DbCommand dc2 = db.GetStoredProcCommand("usp_College_Insert"); db.AddInParameter(dc2, "@CollegeID", DbType.Int32, ); db.AddInParameter(dc2, "@Name", DbType.String, "化工学院"); using (DbConnection conn = db.CreateConnection()) { conn.Open(); DbTransaction trans = conn.BeginTransaction(); try { //添加一个ID为7的学院 db.ExecuteNonQuery(dc1, trans); //添加一个ID为7的学院,主键重复,事务将回滚 db.ExecuteNonQuery(dc2, trans); //提交事务. trans.Commit(); } catch { //回滚 trans.Rollback(); } conn.Close(); } //查看数据库,数据未被添加,说明事务已回滚 ExecuteDataSet_Click(null, null);}
(6) 通过DataSet更新数据库.
///<summary>/// 通过DataSet更新数据库///</summary>privatevoid DataSetUpdate_Click(object sender, EventArgs e){ DataSet productsDataSet =new DataSet(); string sql ="Select * From College"; DbCommand cmd = db.GetSqlStringCommand(sql); string CollegeTableName ="College"; //恢复原始数据 db.LoadDataSet(cmd, productsDataSet, CollegeTableName); //获取数据表格 DataTable dTable = productsDataSet.Tables[CollegeTableName]; //添加一个新信息入DataSet中 DataRow addedRow = dTable.Rows.Add(newobject[] { , "外国语学院" }); //修改一个原有数据 dTable.Rows[]["Name"] ="国教院"; //提供插入,更新,删除存储过程 DbCommand insertCommand = db.GetStoredProcCommand("usp_College_Insert"); db.AddInParameter(insertCommand, "@CollegeID", DbType.Int32, "CollegeID", DataRowVersion.Current); db.AddInParameter(insertCommand, "@Name", DbType.String, "Name", DataRowVersion.Current); DbCommand deleteCommand = db.GetStoredProcCommand("usp_College_Delete"); db.AddInParameter(deleteCommand, "@CollegeID", DbType.Int32, "CollegeID", DataRowVersion.Current); DbCommand updateCommand = db.GetStoredProcCommand("usp_College_Update"); db.AddInParameter(updateCommand, "@CollegeID", DbType.Int32, "CollegeID", DataRowVersion.Current); db.AddInParameter(updateCommand, "@Name", DbType.String, "Name", DataRowVersion.Current); //通过DataSet更新数据库int rowsAffected = db.UpdateDataSet(productsDataSet, CollegeTableName, insertCommand, updateCommand, deleteCommand, Microsoft.Practices.EnterpriseLibrary.Data.UpdateBehavior.Standard); MessageBox.Show("影响的行数:"+ rowsAffected);}
(7) 返回值XML化.
///<summary>/// 返回值XML化///</summary>privatevoid ReturnXML_Click(object sender, EventArgs e){ //使用"FOR XML AUTO"参数使得SQL返回XML格式的信息 SqlDatabase sqldb = (SqlDatabase)DatabaseFactory.CreateDatabase("ConnectionString"); DbCommand cmd = sqldb.GetSqlStringCommand("SELECT * FROM College FOR XML AUTO"); IEnumerable<string> productList; using (var reader = sqldb.ExecuteXmlReader(cmd)) { if (reader.IsStartElement()) { var root = (XElement)XNode.ReadFrom(reader); productList = root.Elements("CollegeID") .Attributes("Name") .Select(a => a.Value).ToArray(); MessageBox.Show(((XElement)root).ToString()); } }}
(8) 将返回的数据对象化.
///<summary>/// DataAsObject///</summary>privatevoid DataAsObject_Click(object sender, EventArgs e){ //将返回的数据对象化 var results = db.ExecuteSprocAccessor<College>("usp_College_LoadAll"); MessageBox.Show(results.ElementAt().ToString());}
(9) 异步访问数据库.
///<summary>/// 异步访问数据库///</summary>privatevoid Async_Click(object sender, EventArgs e){ //创建新的数据库连接,属性必须添加:Asynchronous Processing=true String connectionString =@"server=(local); database=TestDB; Integrated Security=true; Asynchronous Processing=true"; Database Sqldb =new SqlDatabase(connectionString); DbCommand cmd = Sqldb.GetStoredProcCommand("usp_College_LoadbyID"); Sqldb.AddInParameter(cmd, "@CollegeID", DbType.Int32, ); try { IAsyncResult result = Sqldb.BeginExecuteReader(cmd, MyEndExecuteCallback, Sqldb); } catch (Exception ex) { MessageBox.Show(ex.ToString()); }}//当获取完毕执行该函数privatevoid MyEndExecuteCallback(IAsyncResult result){ try { Database Sqldb = (Database)result.AsyncState; IDataReader reader = db.EndExecuteReader(result); College c =new College((int)reader[], (string)reader[]); MessageBox.Show(c.ToString()); } catch(Exception ex) { MessageBox.Show(ex.ToString()); }}