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.NET Forum / Languages / VB.NET / October 2004Sub Dispose or Implementing the Dispose Interface?
In a typical class, do I need to indicate that it implements the IDisposable interface and then create a Dispose method that implements the Dispose required by the IDisposable interface or can I just make a Sub Dispose() and the CLR will know that this is the Dispose method to call when the object falls out of scope? Thanks. The runtime (CLR) never calls the dispose method. It is upto the client using the object to call dispose. There are a couple of exceptions. Read this for more information: http://blogs.msdn.com/clyon/archive/2004/09/21/232445.aspx So whether you just add a Dispose method or implement IDisposable interface, its upto the application using your class to call the dispose method. Ofcourse, it makes more sense to implement IDisposable since that is indeed why the interface is there - for one to write dispose code. If you simply write a Sub Dispose, it could be misleading to someone using your class since one would expect an implementation of IDisposable if one were to follow the standards. hope that helps.. Imran. > In a typical class, do I need to indicate that it implements the > IDisposable interface and then create a Dispose method that implements the [quoted text clipped - 3 lines] > > Thanks. Ok Imran, then let me ask you this... When the GC does eventually collect the garbage, what determines which objects are collected and which are not? Is is simply that any object that is no longer referenced are the ones collected? > The runtime (CLR) never calls the dispose method. It is upto the client > using the object to call dispose. There are a couple of exceptions. Read [quoted text clipped - 19 lines] >> >> Thanks. "Scott M." <NoSpam@NoSpam.com> wrote > Ok Imran, then let me ask you this... > > When the GC does eventually collect the garbage, what determines which > objects are collected and which are not? Is is simply that any object that > is no longer referenced are the ones collected? Its not quite that simple. The GC is good at cleaning up short lived objects, but those that hang around for a while get shoved on 'the back burner' (meaning they don't get tested as often). The GC is also pretty good at managing those long lived objects, but its the middle ground that needs to be addressed. That area is dependant on your own use of memory, so just how often the GC runs, and decides to move things to the 'back burner' is partially dependant on what you're doing.... FWIW: The proper term is 'generations'. Generation 0 items come and go as needed.... So, its those Gen 0 items that are swept away when nothing holds a reference to them. If they survive that first look, then get shoved into the Gen 1 area, and then Gen 2, etc where they don't go looking for memory as often as the Gen 0 area. For a bit more on the GC, you might want to watch the .Net show where one of the CLR's architect was interviewed: http://msdn.microsoft.com/theshow/Episode027/default.asp LFS Scott, As Larry mentioned, collection is a bit more complicated. I think you are confusing a finalize method with the dispose method (I could be wrong though). If an object has a finalizer, it is not collected (when a collection is performed by the GC and it finds that the object is not referenced anymore) but instead is pushed onto a finalization queue so that the runtime can execute the finalize method of the object. And then there is the concept of various generations (0, 1 and 2 in the current framework version). I would suggest you read these 2 excellent articles by Jeffrey Richter on Garbage collection which also talks about finalization and resurrection: http://msdn.microsoft.com/msdnmag/issues/1100/GCI/ http://msdn.microsoft.com/msdnmag/issues/1200/GCI2/default.aspx Also, here is a blog post on dispose dos and don'ts by Chris Lyon which you might be interested in since you are deciding to implement dispose in your class: http://blogs.msdn.com/clyon/archive/2004/09/23/233464.aspx hope that helps.. Imran. > Ok Imran, then let me ask you this... > [quoted text clipped - 25 lines] >>> >>> Thanks. Scott, The framework itself never calls Dispose. C# will call IDisposable.Dispose if you use the object in a Using statement. VB.NET 2002 & 2003 & C#'s For Each statements will call IDisposable.Dispose if its part of a class that implements IEnumerator. Otherwise VB.NET (2002 & 2003) will not call IDisposable.Dispose. VB.NET 2005 (aka Whidbey, due out later in 2005) will add support to VB.NET for the Using statement, the Using statement will call IDisposable.Dispose on the End Using line. Information on VB.NET 2005: http://lab.msdn.microsoft.com/vs2005/ Information on VB.NET's Using statement: http://msdn2.microsoft.com/library/htd05whh.aspx An object falling out of scope never calls Dispose nor IDisposable.Dispose. If you are considering implementing IDisposable, you should also consider implementing Finalize also. The "Implementing Finalize and Dispose to Clean Up Unmanaged Resources" on MSDN: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgenref/html/c pconFinalizeDispose.asp Covers when you should implement Finalize, when you should implement both, and when you should implement just IDisposable. Hope this helps Jay > In a typical class, do I need to indicate that it implements the > IDisposable interface and then create a Dispose method that implements the [quoted text clipped - 3 lines] > > Thanks. Scott, When you use the componenttemplate to create the class, it gives you a complete class where IDisposable setting is completly done for you. In any class that implements IDisposable is the disposing from the resourses used in that class done for you. Cor > In a typical class, do I need to indicate that it implements the > IDisposable interface and then create a Dispose method that implements the [quoted text clipped - 3 lines] > > Thanks. Yes, I know that Cor. My question was about classes that are built from scratch. > Scott, > [quoted text clipped - 13 lines] >> >> Thanks. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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