Recipe 1.7 Connecting to a Named Instance of SQL Server or Microsoft Data Engine (MSDE)

Problem

You want to connect to a named instance of a SQL Server or Microsoft Data Engine (MSDE).

Solution

You need to understand what a SQL Server or MSDE named instance is and how to connect to one. The sample code contains a single event handler:

Connect Button.Click

Creates and opens a connection to a named instance of a SQL Server. Information about the SQL Server is displayed from the properties of the SqlConnection object.

The C# code is shown in Example 1-6.

Example 1-6. File: ConnectNamedInstanceForm.cs

// Namespaces, variables, and constants
using System;
using System.Configuration;
using System.Windows.Forms;
using System.Text;
using System.Data.SqlClient;

//  . . . 

private void connectButton_Click(object sender, System.EventArgs e)
{
    StringBuilder result = new StringBuilder( );

    SqlConnection conn = new SqlConnection(
        ConfigurationSettings.AppSettings["Sql_Msde_ConnectString"]);

    try
    {
        conn.Open( );

        // Return some information about the server.
        result.Append(
            "ConnectionState = " + conn.State + Environment.NewLine +
            "DataSource = " + conn.DataSource + Environment.NewLine +
            "ConnectionState = " + conn.State + Environment.NewLine +
            "ServerVersion=" + conn.ServerVersion +
            Environment.NewLine);
    } 
    catch(Exception ex) 
    {
        MessageBox.Show(ex.Message);
    }
    finally
    {
        conn.Close( );
    }

    result.Append("ConnectionState = " + conn.State);

    resultTextBox.Text = result.ToString( );
}

Discussion

SQL Server 2000 introduced the ability to install multiple copies of SQL Server on a single computer. Only one copy can function as the default instance at any time; it is identified by the network name of the computer on which it is running. All other copies are named instances and are identified by the network name of the computer plus an instance name. The format is <computerName>\<instanceName>. This format is used in the connection string to specify the Data Source attribute for a named instance.

Each instance operates independently of the other instances installed on the same computer. Each instance has its own set of system and user databases that are not shared between instances and it runs within its own security context. The maximum number of instances supported on SQL Server 2000 is 16. The Microsoft Distributed Transaction Coordinator (DTC) and the Microsoft Search services are installed and used simultaneously by every installed instance of SQL Server. Client tools such as Enterprise Manager and Query Analyzer are also shared.

The System.Data.SqlClient class cannot automatically discover the port number of a named instance of SQL Server listening on a port other than the default 1433. To connect to a named instance of SQL Server listening on a custom port, specify the port number following the instance name in the connection string separated by a comma. For, if the named instance msde01 was set up to listen on port 1450, the following connection string might be used:

Data Source=(local)\msde01,1450;Integrated security=SSPI;
    Initial Catalog=Northwind