Yes but it doesn't protect the case when an exception is thrown in cmd.Dispose(). In that case cn.Close() will not be called as Kirk said.
Jim > -----Original Message----- > From: Peter Stephens [mailto:[EMAIL PROTECTED]] > Sent: Friday, May 03, 2002 5:13 PM > To: [EMAIL PROTECTED] > Subject: [DOTNET] try...finally vs. nested using statements > WAS: From C# > to VB.NET > > > My sample below which uses try...finally does handle the case > properly if > there is an exception thrown in either the command constructor or the > connection creation. > > For example if the connection is properly constructed with no > exceptions > then cn is not null and cn.Close() will be closed no matter > how the routine > exits (by return or by exception). If an exception occurs > during connection > creation then cn is null and cn.Close() will not be called. > > The main advantage to using nested using statements is that the using > statement allows putting your construction and cleanup code > in one place (at > the top of the using block). > > There is a downside though. Each using statement creates a > new try...finally > construct. Look through ILDASM and you will see a > try...finally block for > every nested using statement. While try...finally overhead > might be minimal, > it still requires more overhead than hand coding the > try...finally block. > > It would be nice if the using statement allowed > initialization of multiple > types at once! *sigh* > > -- > Peter > > > Kirk Jackson spake: > > > > The reason 'using' is useful, is that you don't need to worry > > about an exception being thrown from your first dispose call (as > > if there is an exception, you'd still want to call cn.Close) > > > > Kirk > > > > -----Original Message----- > > From: Peter Stephens [mailto:[EMAIL PROTECTED]] > > Sent: Thursday, 2 May 2002 8:03 p.m. > > To: [EMAIL PROTECTED] > > Subject: Re: [DOTNET] From C# to VB.NET > > > > > > Thank you Mattias, > > > > I had never considered that multiple using statements before the > > code block were valid. I certainly haven't seen it used like this > > before. Your second technique is also interesting except that it > > requires the overhead of the cast. > > > > My typical pattern is: > > > > SqlConnection cn = null; > > SqlCommand cmd = null; > > try > > { > > cn = new SqlConnection(...); > > cmd = cn.CreateCommand(); > > > > // Do something > > } > > finally > > { > > if(cmd != null) cmd.Dispose(); > > if(cn != null) cn.Close(); > > } > > > > This keeps everything strongly typed from the start. Still your > > first technique is intriguing in that it also eliminates the > > chance of forgetting the cleanup code in the finally block... > > > > -- > > Peter > > > > > > > Mattias Sjögren spake: > > > > > > Peter, > > > > > > >I will often use the try ... finally pattern in C# if there is > > > more than one > > > >type of resource to clean up. The using statement only supports > > > one type at > > > >a time. > > > > > > Yes, but you can easily nest them > > > > > > using ( DisposableType1 d1 = new DisposableType1() ) > > > using ( DisposableType2 d2 = new DisposableType2() ) > > > using ( DisposableType3 d3 = new DisposableType3() ) { > > > // ... > > > } > > > > > > or > > > > > > using ( IDisposable d1 = new DisposableType1(), d2 = new > > > DisposableType2() ) { > > > DisposableType1 dt1 = d1 as DisposableType1; > > > DisposableType2 dt2 = d2 as DisposableType2; > > > // ... > > > } > > > > > > > > > Mattias > > > > You can read messages from the DOTNET archive, unsubscribe from > > DOTNET, or subscribe to other DevelopMentor lists at > http://discuss.develop.com. > > You can read messages from the DOTNET archive, unsubscribe > from DOTNET, or > subscribe to other DevelopMentor lists at http://discuss.develop.com. > > You can read messages from the DOTNET archive, unsubscribe > from DOTNET, or > subscribe to other DevelopMentor lists at http://discuss.develop.com. > You can read messages from the DOTNET archive, unsubscribe from DOTNET, or subscribe to other DevelopMentor lists at http://discuss.develop.com.
