Is it necessary to call "Close" when within 'using' statement upon early process termination?

Question

If I initialize a class with the Using statement, is it necessary to call it's Close method upon early termination?

Using xmlstream As New MemoryStream()
    Try
        'Do runtime operation

    Catch ex As Exception
        Console.WriteLine("Could not fill dataset.  REASON: " & ex.Message)
        xmlstream.Close()  '<-  NECESSARY????
        Environment.Exit(-1) '<- Early termination!
    End Try
    'DO STUFF
End Using

Answer 1

Not it is not necessary. According to the IDisposable.Dispose Method documentation

"The using statement automatically closes the stream and calls Dispose on the object when the code that is using it has completed"

Having said that it is not a good idea to have Environment.Exit within a Using block as this does not call Close, or indeed Dispose. Instead you should refactor this as a function that returns True or False and act on that return value to decide whether to Exit or not