The ODBC.NET data
provider installation adds the Microsoft.Data.Odbc namespace to the namespace, which defines the classes for ODBC data providers. To use the ODBC.NET data provider, you must add a using statement for the Microsoft.Data.Odbc namespace to your application:
using Microsoft.Data.Odbc;
You've seen how to use the SQL and OleDb data providers in previous articles. Working with the ODBC data provider is no different from working with the Sql and OleDb data providers. Unlike the sql and OleDb data providers, however, the ODBC data provider is defined in the Microsoft.Data.Odbc namespace. You must add a reference to this namespace before you start using the ODBC data provider classes.
The ODBC data provider defines similar classes and a class hierarchy as the Sql and Oledb data providers. Further, you can use the ODBC classes as you've used the SQL and OleDb classes. Table 11-1 defines the ODBC.NET data provider classes
Table 11-1: The ODBC.NET Data Provider Classes
|
CLASS
|
DESCRIPTION
|
|
OdbcCommand
|
Similar to OleDbCommand and SqlCommand, this class represents an SQL statement or stored procedure to execute against adatasource.
|
|
OdbcCommandBuilder
|
Similar to OleDbCommandBuilder and SqlCommandBuilder, this class automatically generates select, insert, update, and delete SQL commands.
|
|
OdbcConnection
|
Represents a connection.
|
|
OdbcDataAdapter
|
Represents a data adapter.
|
|
OdbcDataReader
|
Represents a data reader.
|
|
OdbcError
|
Represents errors and warnings.
|
|
OdbcErrorCollection
|
Represents collection of errors and warnings.
|
|
OdbcException
|
Represents an ODBC exception class.
|
|
OdbcParameter
|
Represents an ODBC parameter.
|
|
OdbcParameterCollection
|
Represents a parameter collection.
|
|
OdbcTransaction
|
Represents a transaction.
|
As you can see from table 11-1, the ODBC data provider has connection, command, data adapter, parameter, exception, and errors, command builder, data reader, transaction, and other classes similar to the Sql and OleDb data providers. To use the ODBC data provider classes, you create a connection object, fill data from the connection to a data adapter or a data reader, and then display the data.
Now I'll show you an example of how to access data from a data source using the ODBC data provider. In this example, I'll use the access 2000 Northwind database as the data source.
Before creating a connection, the first thing you need to understand is the connection string. The connection string for OdbcConnection contains a data source driver and the data source path with an optional user ID and password. Optionally, you can also use an ODBC Data Source Name (DSN) as a connection string. You create a DSN from the ODBC Administration.
The connection string for an Oracle database looks like the following:
Driver={Microsoft ODBC for Oracle}; Server=Oracle8i7;UID=odbcuser;PWD=odbc$5xr
The connection string for a Microsoft Access Database looks like the following:
Driver={Microsoft Access Driver (*.mdb)};
DBQ=c:\Northwind.mdb
The connection string for an Excel database looks like the following:
Driver={Microsoft Excel Driver (*.xls)};
DBQ=c:\bin\book1.xls
The connection string for a Text database looks like the following:
Driver={Microsoft Text Driver (*.txt; *.csv)};
DBQ=c:\
You can use any data source name (DSN) by using the following connection string:
DSN=dsnname
The connection string for a SQL Server database looks like the following:
"DRIVER={SQL Server};
SERVER=MyServer;UID=sa;PWD=Qvr&77xk;DATABASE= northwind;";
Listing 11-1 reads data from Northwind database and shows the results on the console. In this sample, I created a console application to test the code. As you can see from listing 11-1, first I included the Microsoft.Data.Odbc namespace. After that I created an OdbcConnection object with the Microsoft Access ODBC driver and the Northwind database. The next step was to create an OdbcCommand object and call the ExecuteReader method, which returns OdbcDataReader. After that I read data from the data reader and displayed and the results on the console.
Listing 11-1: Reading data from Northwind using the ODBC data provider
Imports Microsoft.Data.Odbc
Namespace FirstODBCSamp
Class Class1
Private Shared Sub Main(ByVal args As String())
' Build a connection and SQL strings
Dim connectionString As String = "Driver={Microsoft Access Driver (*.mdb)};DBQ=c:\Northwind.mdb"
Dim SQL As String = "SELECT * FROM Orders"
' Create connection object
Dim conn As New OdbcConnection(connectionString)
' Create command object
Dim cmd As New OdbcCommand(SQL)
cmd.Connection = conn
' Open Connection
conn.Open()
' Call command's ExecuteReader
Dim reader As OdbcDataReader = cmd.ExecuteReader()
' Read the reader and display results on the console
While reader.Read()
Console.Write("OrderID:" + reader.GetInt32(0).ToString())
Console.Write(" ,")
Console.WriteLine("Customer:" + reader.GetString(1).ToString())
End While
' Close reader and connection
reader.Close()
conn.Close()
End Sub
End Class
End Namespace
The output of listing 11-1 looks like figure 11-7.
Figure 11-7: The output of Listing 11-1