How do I dispose an IDisposable object if the using statement throws an exception?

Question

How can I make sure in the following code snippet that IDataReader is disposed of if ExecuteReader throws an exception?

using (IDataReader rdr = cmd.ExecuteReader())
{
    // use it
}

It makes sense to me that the using syntatic sugar does not call Dispose (since there is no instance to call it on). However, how can I be sure that the scarce resources that are normally allocated by classes that implement IDisposable will be releases?

Answer 1

If ExecuteReader, in your example, throws an exception it never returns anything. It is then up to the implementation of ExecuteReader to dispose of anything created before the exception.