Closing a conneciton in the “unload” method

Question

I have inherited a web framework whereby the previous developer has opened and closed his database connections in the init/unload methods of the page life cycle. Essentially

Answer 1

A (very) quick test (VS2010 web server, .net v4) has shown me that the Unload event is called when an unhandled exception is raised (at least if raised in Page_Load), so the principle looks like it should work.

The pattern as listed in the example is only dispose'ing the connection if the connection was open.

As _conn is protected, pages descended from BasePage can interact with _conn and modify its value. There are two ways for descendant classes to break the pattern:

1. Call _conn.Close() directly. If the connection is not open, it is not disposed in EndConnection.

2. Modify the value of _conn by either setting it to null or assigning a new instance of DBConnection to it.

Consider changing your EndConnection method, so that _conn is always disposed.

private void EndConnection(object sender, EventArgs e)
{
    if (_conn == null)
    {
       return;
    }
    if (_conn.Connection.State == ConnectionState.Open)
    {
         _conn.Close();
    }
    _conn.Dispose(); // always dispose even if not actually open. It may have been closed explicitly elsewhere.
}

Case 2 can't be caught by EndConnection. Consider making _conn private and providing a getter property:

private DBConnection _conn;

protected DBConnection Connection {
     get 
     {
         return _conn;
     }
}

which prevents descendant classes from changing the value of _conn.

Lastly, is DBConnection a class of your own? I only ask as you quote "_conn.Connection.State" rather than just _conn.State. If so, just double check that the Dispose method of DBConnection disposes its Connection instance correctly.