When working with C# applications that connect to SQL Server, you might encounter situations where the connection string references a specific instance name (localhost\foobar in your case) while your development environment uses a different instance name (localhost\developer_2005). Rather than modifying application configuration files, creating a SQL Server alias provides a cleaner solution.

The most reliable method is using SQL Server Configuration Manager:

1. Open SQL Server Configuration Manager
2. Navigate to: SQL Native Client Configuration → Aliases
3. Right-click → New Alias
4. Configure with these values:
   - Alias Name: foobar
   - Port No: (leave blank for named instances)
   - Protocol: TCP/IP
   - Server: localhost\developer_2005

For older systems or when Configuration Manager isn't available:

1. Run cliconfg.exe from command line
2. Go to the Alias tab
3. Click Add
4. Set:
   - Server alias: foobar
   - Network libraries: TCP/IP
   - Connection parameters: localhost\developer_2005

Test your alias using SQLCMD:

sqlcmd -S foobar -E

Or in C# code:

using (var connection = new SqlConnection("Server=foobar;Database=barfoo;Integrated Security=True"))
{
    connection.Open();
    // Connection successful if alias works
}

• 32-bit vs 64-bit: Ensure you configure aliases in both 32-bit and 64-bit Configuration Manager if needed
• Service restart: Some changes may require restarting the SQL Server service
• Protocol order: Check the "Client Protocols" section to ensure TCP/IP is enabled and prioritized

For automation scenarios, you can create aliases via PowerShell:

$smo = 'Microsoft.SqlServer.Management.Smo.'
Add-Type -AssemblyName "Microsoft.SqlServer.Smo"

$server = New-Object ($smo + 'Server') 'localhost\developer_2005'
$server.ConnectionContext.ServerInstance = 'foobar'
$server.ConnectionContext.Connect()

If connections fail after alias setup:

1. Verify SQL Server Browser service is running
2. Check firewall settings for SQL Server ports
3. Test with both machine name and localhost variations
4. Examine SQL Server error logs for connection attempts

When developing applications that connect to SQL Server, we often encounter environment discrepancies between development and production. In this case, your C# application expects to connect to localhost\foobar, but your actual development instance is named developer_2005. Let me show you the proper way to create an alias at the system level.

The most reliable approach is using SQL Server Configuration Manager:

1. Open SQL Server Configuration Manager
2. Navigate to: SQL Native Client Configuration → Aliases
3. Right-click → New Alias
4. Configure with these values:
   - Alias Name: foobar
   - Port No: [blank]
   - Protocol: TCP/IP
   - Server: localhost\developer_2005

After setting up the alias, test it with this connection string:

string connectionString = @"Data Source=localhost\foobar;
Initial Catalog=barfoo;
Integrated Security=True;";

using (SqlConnection connection = new SqlConnection(connectionString))
{
    try 
    {
        connection.Open();
        Console.WriteLine("Successfully connected via alias!");
    }
    catch (Exception ex)
    {
        Console.WriteLine($"Connection failed: {ex.Message}");
    }
}

For scenarios where you need broader redirection, you can modify the Windows hosts file:

# Located at C:\Windows\System32\drivers\etc\hosts
127.0.0.1   sql-foobar

Then use this connection string:

Data Source=sql-foobar\developer_2005;

• Aliases are client-side configurations - they won't affect other developers' machines
• For production deployments, consider using connection string transformations in your deployment pipeline
• Always verify the alias works in SQLCMD or SSMS before testing in application code

If the alias doesn't work immediately:

1. Restart the SQL Server service
2. Ensure the SQL Server Browser service is running
3. Check for firewall rules blocking the connection
4. Verify the alias appears in registry at: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Client\ConnectTo