This class represents a connection to a data source, which can be
opened using the Open( ) method or closed using
Close( ) . No work can be performed while a
connection is closed; however, some objects (such as data adapters)
automatically open and close their connection as required. A data
provider derives its own Connection class (such as
System.Data.SqlClient.SqlConnection ) that
implements this interface.
With most data providers, you need to set some basic information
(such as the initial database, server, and user login account) in the
ConnectionString property before you attempt to
open a connection. The connection string information differs from
provider to provider. All connection strings arrange their
information in a series of name-value pairs delimited by semicolons.
Other than ConnectionString , the other
IDbConnection properties are read-only. Chapter 3 provides connection string examples for
several provider types and a list of supported parameters.
The IDbConnection interface also defines a
BeginTransaction( ) method, which initiates a SQL
transaction and returns an IDbTransaction object
that allows you to commit or roll back the transaction. You can also
use ChangeDatabase( ) to work with the tables in a
different database in the same data source, and
CreateCommand( ) to generate a generic
IDbCommand instance linked to the current
connection. You don't need to use
CreateCommand( ) ; you can instantiate the
appropriate provider-specific Command object.
However, the CreateCommand( ) method is useful
when you need to write provider-agnostic ADO.NET code. Even though it
returns the appropriate provider-specific Command
object, you can interact with it solely through the
IDbConnection and IDbCommand
interfaces, freeing your code from provider-specific details.
public interface IDbConnection : IDisposable {
// Public Instance Properties
public string ConnectionString{set; get; }
public int ConnectionTimeout{get; }
public string Database{get; }
public ConnectionState State{get; }
// Public Instance Methods
public IDbTransaction BeginTransaction( );
public IDbTransaction BeginTransaction(IsolationLevel il);
public void ChangeDatabase( string databaseName);
public void Close( );
public IDbCommand CreateCommand( );
public void Open( );
}
