1、第 17 章 使用 DataReader 物件讀取資料庫 第 17 章 使用 DataReader 物件讀取資料庫 物件讀取庫課件物件讀取庫課件無論使用哪種 .NET Framework 資料提供者存取資料庫，其步驟均相同，只是使用的物件不同：建立資料連接執(zhí)行 SQL 命令並傳回結(jié)果讀取執(zhí)行結(jié)果 無論使用哪種 .NET Framework 資料提供者存取資17-2建立資料連接 無論哪種資料來源，建立資料連接的語法均相同，您可以使用下列兩種語法為 OLE DB 相容資料庫建立資料連接：Dim objConn As New OleDbConnection()Dim objConn As New O

2、leDbConnection(connectionString)17-2建立資料連接 無論哪種資料來源，建立資料連接的語法Connection 物件的屬性 ConnectionString= ConnectionTimeout DataSource Driver PacketSize Provider ServerVersion State Connection 物件的屬性 Connection 物件的方法BeginTransaction() Close() CreateCommand() Open() Connection 物件的方法Connection 物件的事件StateChange C

3、onnection 物件的事件Ch17Connection_01_Access.aspx01:02:03:04:05: Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)06: Dim objConn As New OleDbConnection()07: objConn.ConnectionString = Provider=Microsoft.Jet. OLEDB.4.0; & Data Source= & _ Server.MapPath(/App_Data/Friend.mdb)08: objConn.O

4、pen()09: objConn.Close()10: End Sub11:Ch17Connection_01_Access.aspweb.config web.configweb.config web.config若要在程式碼中取得特定的連接設(shè)定，可以使用 ConfigurationManager 類別的靜態(tài)方法 ConnectionStrings()，其語法如下：Dim setting As ConnectionStringSettings = ConfigurationManager.ConnectionStrings(name)例如下面的敘述可以從 web.config 組態(tài)檔取得識別

5、名稱為 OLEDB_Friend 的連接設(shè)定：Dim setting As ConnectionStringSettings = ConfigurationManager.ConnectionStrings(OLEDB_Friend)若要在程式碼中取得特定的連接設(shè)定，可以使用 ConfigurCh17Connection_02_Access.aspx Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) 取得 web.config 組態(tài)檔的資料連接設(shè)定 Dim setting As ConnectionString

6、Settings = _ConfigurationManager.ConnectionStrings(OLEDB_ Friend)Ch17Connection_02_Access.asp 建立 Connection 物件 Dim objConn As New OleDbConnection() objConn.ConnectionString = setting.ConnectionString 開啟資料連接 objConn.Open() 關(guān)閉資料連接 objConn.Close() End Sub 建立 Connection 物件17-3執(zhí)行 SQL 命令 無論哪種資料來源，建立 Comma

7、nd 物件的語法均相同，您可以使用下列四種語法為 OLE DB 相容資料庫建立 Command 物件：Dim objCmd As New OleDbCommand()Dim objCmd As New OleDbCommand(sql)Dim objCmd As New OleDbCommand(sql, connection)Dim objCmd As New OleDbCommand(sql, connection, transaction) 17-3執(zhí)行 SQL 命令 無論哪種資料來源，建立 ComCommand 物件的屬性CommandText= CommandTimeout=n Co

8、mmandType=StoredProcedure|TableDirect|Text Connection= Parameters Transaction= Command 物件的屬性Command 物件的方法Cancel() Clone() ExecuteNonQuery() ExecuteReader() ExecuteScalar() Command 物件的方法Ch17Command_Access.aspx Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) 取得 web.config 組態(tài)檔的資料連接設(shè)定

9、 Dim setting As ConnectionStringSettings = _ ConfigurationManager.ConnectionStrings(OLEDB_Friend) 建立資料連接 Dim objConn As New OleDbConnection()Ch17Command_Access.aspx objConn.ConnectionString = setting.ConnectionString 開啟資料連接 objConn.Open() 使用 Command 物件執(zhí)行 SQL 命令 Dim strSQL As String = Delete From 擇友俱

10、樂部 Where 姓名=幻影小雨貓 Dim objCmd As New OleDbCommand(strSQL, objConn) objCmd.ExecuteNonQuery() 關(guān)閉資料連接 objConn.Close() End Sub objConn.ConnectionString =17-4使用 DataReader 物件讀取資料 我們可以透過 Command 物件的 ExecuteReader() 方法建立 DataReader 物件，如下所示：Dim objReader As OleDbDataReader = objCmd.ExecuteReader()Dim objRead

11、er As SqlDataReader = objCmd.ExecuteReader()Dim objReader As OdbcDataReader = objCmd.ExecuteReader()Dim objReader As OracleDataReader = objCmd.ExecuteReader()17-4使用 DataReader 物件讀取資料 我們可以DataReader 物件的屬性FieldCount HasRows IsClosed Item(name|ordinal) DataReader 物件的屬性DataReader 物件的方法Close() GetBoolean

12、(ordinal) GetDataTypeName(ordinal) GetFieldType(ordinal) GetName(ordinal) GetOrdinal(name) GetValue(ordinal) GetValues(values) IsDBNull(ordinal) Read() DataReader 物件的方法物件讀取庫課件Ch17DataReader_01_Access.aspx01:02:03:04:05: Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)06: 取得 web.con

13、fig 組態(tài)檔的資料連接設(shè)定07: Dim setting As ConnectionStringSettings = _ ConfigurationManager.ConnectionStrings(OLEDB_Friend)08:09: 建立資料連接10: Dim objConn As New OleDbConnection(setting.ConnectionString)Ch17DataReader_01_Access.asp11:12: 開啟資料連接13: objConn.Open()14:15: 建立 DataReader 物件16: Dim objCmd As New OleDb

14、Command(Select * From 擇友俱樂部, objConn)17: Dim objReader As OleDbDataReader = objCmd.ExecuteReader()18: 讀取並顯示資料19: Dim I As Integer20: Response.Write() 21: For I = 0 To objReader.FieldCount 122: Response.Write( & objReader.GetName(I) & )23: Next11:24: Response.Write() 25: While objReader.Read()26: Res

15、ponse.Write()27: For I = 0 To objReader.FieldCount - 128: Response.Write( & objReader.Item(I).ToString() & )29: Next30: Response.Write()31: End While32: Response.Write()33:34: 關(guān)閉 DataReader 物件與資料連接35: objReader.Close()36: objConn.Close()37: End Sub38: 24: Response.Write()17-5使用 Connection 物件的事件 Conn

16、ection 物件有一個名稱為 StateChange 的事件，除了 Web 伺服器控制項之外，使用任何事件都必須依照如下形式進(jìn)行宣告：AddHandler EventName, New EventHandler(AddressOf ProcedureName)17-5使用 Connection 物件的事件 ConneCh17StateChange_Access.aspx01:02:03:04:05: Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)06: 取得 web.config 組態(tài)檔的資料連接設(shè)定07: Dim setting As ConnectionStringSettings = _ ConfigurationManager.ConnectionStrings(OLEDB_Friend)08: Dim objConn As New OleDbConnection(setting.ConnectionString)09: AddHandler objConn.StateChange, _ New StateChangeEventHandler(AddressOf Connection_StateChange)Ch17StateChange_Access.aspx10: obj