ADO.NET in a Nutshell

Connection Object Overview

The Connection object, like all provider-specific ADO.NET objects, comes in more than one version. You use the version that’s tailored for your specific data source. Here are two examples:

• System.Data.SqlClient.SqlConnection allows you to connect to a SQL Server database (Version 7.0 or later).

• System.Data.OleDb.OleDbConnection allows you to connect to almost any data source with an associated OLE DB provider.

Every Connection object that accesses relational databases implements the common System.Data.IDbConnection interface. By looking at the IDbConnection interface, you’ll quickly see the small set of properties and methods that every Connection object is guaranteed to support (see Tables 3-1 and 3-2). The most important of these are the Close( ) and Open( ) methods, and the ConnectionString property, which specifies a variety of options about the data source and how to connect to it. All IDbConnection properties are read-only, except ConnectionString.

Table 3-1. IDbConnection properties

Member	Description
ConnectionString	A string with name-value pairs of connection settings. These settings often include information such as the user to log in and the location of the database server. This is the only writeable property.
ConnectionTimeout	The time to wait for a connection to open before failing with a provider-specific exception (such as SqlException or OleDbException). The default is 15 seconds; 0 waits indefinitely. This value must be set through ...