Tài liệu Connecting to an ODBC Data Source ppt

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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 /> for .NET
Framework Version 1.0.

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