Tài liệu Connecting to an ODBC Data Source ppt

[ Team LiB ] Recipe 1.1 Connecting to an ODBC Data Source Problem You want to access your data source using an ODBC provider from your .NET application. Solution Use the ODBC .NET data provider to access data exposed through an ODBC driver. The sample code contains a single event handler: Connect Button.Click Creates an OdbcDataAdapter and uses it to fill a DataTable with the Category table from the Northwind sample database. The default view of the table is bound to a data grid on the form. The C# code is shown in Example 1-1 . Example 1-1. File: OdbcConnectForm.cs // Namespaces, variables, and constants using System; using System.Configuration; using System.Data; using System.Data.Odbc; // . . . private void connectButton_Click(object sender, System.EventArgs e) { // Create the DataAdapter. String sqlSelect = "SELECT CategoryID, CategoryName, Description " + "FROM Categories"; OdbcDataAdapter da = new OdbcDataAdapter(sqlSelect, ConfigurationSettings.AppSettings["Odbc_ConnectString"]); // Create the table, fill it, and bind the default view to the grid. DataTable dt = new DataTable( ); da.Fill(dt); dataGrid.DataSource = dt.DefaultView; } Discussion The ODBC .NET data provider communicates with native ODBC drivers through COM interop (.NET's interoperability layer for COM). The following ODBC providers are guaranteed to be compatible with the ODBC.NET data provider: • Microsoft SQL Server ODBC Driver • Microsoft ODBC Driver for Oracle • Microsoft Access (Jet) ODBC Driver The .NET data provider for ODBC connects to ODBC data sources through the OdbcConnection object. The ODBC driver connection string is specified using the ConnectionString property. It includes settings needed to establish the connection to the data source. The connection string format closely matches the ODBC connection string format. Additionally, you can specify an ODBC data source name (DSN) or file DSN by setting the ConnectionString attribute to "DSN=myDSN" or "FileDSN=myFileDSN". For more information about specifying ODBC connection strings, see the topic "SQLDriverConnect" in the ODBC Programmer's Reference within MSDN Library. Visual Studio also supports creating ODBC data source connections visually: • Create a data connection in Server Explorer and drag it onto a form or design surface. Configure the OdbcConnection object that appears in the component tray. • Drag an OdbcConnection from the Data tab of the Toolbox onto a form or design surface. Configure the ConnectionString property in the Properties window of the OdbcConnection object that appears. The .NET ODBC data provider requires a reference to the System.Data.Odbc namespace in .NET Framework Version 1.1. In Version 1.0, the namespace is Microsoft.Data.Odbc. Add a .NET Reference to Microsoft.Data.Odbc.dll for a .NET Framework Version 1.0 project. The .NET ODBC .NET data provider ships with .NET Framework Version 1.1. The data provider can be downloaded from http://msdn.microsoft.com/downloads for .NET Framework Version 1.0. [ Team LiB ] . 1.1 Connecting to an ODBC Data Source Problem You want to access your data source using an ODBC provider from your .NET application. Solution Use the ODBC. .NET data provider to access data exposed through an ODBC driver. The sample code contains a single event handler: Connect Button.Click Creates an OdbcDataAdapter