Does Dispose method still get called when Exception is thrown inside of Using statment?

Question

In the example below, is connection going to close and dispose when exception is thrown if it is within using statement?

using (var conn = new SqlConnection("..."))
{
    conn.Open();
    // stuff happens here and exception is thrown...
}

I know this code below will make sure that it does, but I'm curious how using statment does it.

var conn;
try
{
    conn = new SqlConnection("...");
    conn.Open();
    // stuff happens here and exception is thrown...
}
// catch it or let it bubble up
finally
{
    conn.Dispose();
}

Related:

http://stackoverflow.com/questions/141204/what-is-the-proper-way-to-ensure-a-sql-connection-is-closed-when-an-exception-is

Answer 1

Yes, using wraps your code in a try/finally block where the finally portion will call Dispose() if it exists. It won't, however, call Close() directly as it only checks for the IDisposable interface being implemented and hence the Dispose() method.

See also:

• http://stackoverflow.com/questions/220234/intercepting-an-exception-inside-idisposable-dispose
• http://stackoverflow.com/questions/141204/what-is-the-proper-way-to-ensure-a-sql-connection-is-closed-when-an-exception-is
• http://stackoverflow.com/questions/149609/c-using-syntax
• http://stackoverflow.com/questions/317184/c-using-keyword-when-and-when-not-to-use-it
• http://stackoverflow.com/questions/278902/using-statement-vs-try-finally
• http://stackoverflow.com/questions/212198/what-is-the-c-using-block-and-why-should-i-use-it
• http://stackoverflow.com/questions/513672/disposable-using-pattern
• http://stackoverflow.com/questions/376068/does-end-using-close-an-open-sql-connection

Answer 2

This is how reflector decodes the IL generated by your code:

private static void Main(string[] args)
{
    SqlConnection conn = new SqlConnection("...");
    try
    {
        conn.Open();
        DoStuff();
    }
    finally
    {
        if (conn != null)
        {
            conn.Dispose();
        }
    }
}

So the answer is yes, it will close the connection if

DoStuff()

throws an exception.