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[0];
}

 

 

(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, 5);

    dataGridView1.DataSource = db.ExecuteDataSet(dc).Tables[0];
}

 

(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, 7);
    db.AddInParameter(dc1, "@Name", DbType.String, "文旅学院");

    DbCommand dc2 = db.GetStoredProcCommand("usp_College_Insert");

    db.AddInParameter(dc2, "@CollegeID", DbType.Int32, 7);
    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[] { 8, "外国语学院" });

    //修改一个原有数据
    dTable.Rows[0]["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(0).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, 1);

    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[0], (string)reader[1]);

        MessageBox.Show(c.ToString());
    }
    catch(Exception ex)
    {
        MessageBox.Show(ex.ToString());
    }
}