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In both JDBC and ADO.NET, a connection to the underlying data source is represented by a Connection object, which provides the starting point for all subsequent interaction with the data source.

The IDbConnection interface is the ADO.NET equivalent of the JDBC Connection interface. An explicit instance of the JDBC Connection interface is obtained via the getConnection factory method of the java.sql.DriverManager or javax.sql.DataSource interface. IDbConnection instances are created using constructors; the programmer must explicitly instantiate the appropriate implementation for the underlying data source. The IDbConnection implementation classes accept a connection string as a constructor argument containing connection configuration parameters in the form of name/value pairs separated by semicolons, similar in nature to a JDBC URL. The connection string can be passed as an argument to the IDbConnection implementation class constructor or set via the ConnectionString property after construction. Invalid or missing values in the connection string cause a System.ArgumentException to be thrown.

Once the IDbConnection has been created, it's prepared for use by calling the Open method. This method should be called only once for each connection; repeated calls to the Open method cause a System.InvalidOperationException to be thrown. The state of a Connection can be determined using the IDbConnection.State property. State returns one of the following values from the System.Data.ConnectionState enumeration: Broken, Open, or Closed. The DBDemo.Connect method creates and opens an IDbConnection to a Microsoft SQL Server with the name contained in the sqlServerName field.

private void Connect() { // Create a connection to the specified SQL Server using // a database named MyDatabase and integrated Windows security string conStr = "Data Source=" + sqlServerName + " ; Database=MyDataBase;" + " Integrated Security=SSPI"; sqlCon = new SqlConnection(conStr); // Open the SQL Server Connection sqlCon.Open(); }

Comments The application name to use for the connection. Defaults to .Net SqlClient Data Provider. The number of seconds the connection will try to connect to the data source before failing and generating an error. Defaults to 15 seconds. The name or address of the Microsoft SQL Server instance with which to connect. Database The name of the database to use. Integrated Determines whether the connection is secure. Valid values are true, false, and Security sspi, which is equivalent to true. Defaults to false. Packet Size Size in bytes of the network packets used to communicate with SQL Server. Defaults to 8192. Password The user password to use to connect to the SQL Server. User ID The user name to use to connect to the SQL Server. Workstation ID The workstation name to use for the connection. Defaults to the local computer name.

If implemented by the data source vendor, JDBC Connection instances obtained via the DataSource.getConnection method will be pooled, meaning that a small number of connections will be shared to service requests from a larger number of clients. All connections obtained through the .NET SQL and OLE Data Provider implementations are pooled by default. The native OLE DB implementation provides connection pooling for the

OLE Data Provider, and the SQL Provider implements pooling directly in the .NET classes; consult the .NET documentation for details of the pooling strategy. Table 16-4 summarizes the connection string parameters that can be used to specify the default connection pooling behavior of the SqlConnection class.

Comments A connection is destroyed if it is older than this value in seconds when it is returned to the pool. The default value of 0 (zero) seconds prevents connections from being destroyed. If true, the connection is reset when taken from the pool; if false, it is not Connection reset, avoiding the additional communication with the server. Defaults to true. Reset Max Pool Size The maximum number of connections allowed in the pool. Defaults to 100. Min Pool Size The minimum number of connections allowed in the pool. Defaults to 0 (zero). When true, the new connection object is taken from or created in an Pooling appropriate pool; otherwise, the connection is created independent of pooling. Defaults to true.