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.NET Forum / Windows Forms / WinForm General / August 2004Dispose a managed object
Hi there, can someone clarify something for me please? I have a windows form class that contains a Font private member which is initialised (new'ed) in the forms constructor. The font is used in formatting a richtextbox control. Do I have to dispose of the font member in the forms Dispose method or does this happen automatically because it is a member of the form? I think I need to call font.Dispose on it but I wanted some confirmation on this first. If I do have to call Dispose on it should I do this in the form's Dispose method? Regards Graham Allwood * "Gravy" <Gravy@discussions.microsoft.com> scripsit: > can someone clarify something for me please? I have a windows form class > that contains a Font private member which is initialised (new'ed) in the [quoted text clipped - 5 lines] > this first. If I do have to call Dispose on it should I do this in the > form's Dispose method? The call to the 'Dispose' method is not mandatory. If the GC is about to destoy the object, it will be disposed automatically.  SignatureM S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://dotnet.mvps.org/dotnet/faqs/ So calling Dispose is like being a good citizen, it's not mandatory but it does free resources ASAP? Graham >* "Gravy" <Gravy@discussions.microsoft.com> scripsit: >> can someone clarify something for me please? I have a windows form class [quoted text clipped - 11 lines] > The call to the 'Dispose' method is not mandatory. If the GC is about > to destoy the object, it will be disposed automatically. * "Gravy" <Gravy@discussions.microsoft.com> scripsit: > So calling Dispose is like being a good citizen, it's not mandatory but it > does free resources ASAP? That's true. By calling 'Dispose', unmanaged resources that are held by the object are released, for example file handles, database connections, GDI objects, ... These objects would not be freed until the GC destroys the object. If, for example, the number of GDI handles is limited, calling 'Dispose' to internally free the handles that are not needed any more, will result in higher scalability. SignatureM S Herfried K. Wagner M V P <URL:http://dotnet.mvps.org/> V B <URL:http://dotnet.mvps.org/dotnet/faqs/ Just a fair warning that in some cases not calling Dispose() on unmanaged resources can have detrimental impact on your application (for example on database connections, or components derived from System.EnterpriseServices). That being said - I would agree - not disposing your Font is probably not going to have a big impact on your application, especially if in your scenario the Font wouldn't be disposed until the form is closed. For more information on Dispose, see the following MSDN Articles: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cp conimplementingdisposemethod.asp http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpgenref/html/c pconFinalizeDispose.asp >* "Gravy" <Gravy@discussions.microsoft.com> scripsit: >> So calling Dispose is like being a good citizen, it's not mandatory but [quoted text clipped - 7 lines] > calling 'Dispose' to internally free the handles that are not needed any > more, will result in higher scalability. >The call to the 'Dispose' method is not mandatory. If the GC is about >to destoy the object, it will be disposed automatically. This statement is a bit misleading. The GC *never* calls Dispose on an object. The GC will call an object's finalize method (which should, in turn, call Dispose). Note, this does not happen when the GC is "about to destroy an object". When an object is no longer referenced, it is considered garbage. The GC will reclaim that memory the next time it performs a collection, unless the object has a finalizer, in which case, it is put on the finalization queue, and its finalizer run on a seperate thread at an undetermined time in the future. After the finalizer is run, assuming the object has not been resurrected, its memory is reclaimed. The GC has no knowledge of unmanged resources (file handles, GDI handles, socket connections, etc), so they must be explicitly released in a Dispose method, and in a finalizer as a fall-back (see the Dispose pattern links further down this thread). What that means for you, if you have a object that implements a Dispose method, call it as soon as you're finished with the object. This will release the unmanaged resources sooner than waiting for the finalizer to be run. Hope that helps -Chris SignatureThis posting is provided "AS IS" with no warranties, and confers no rights. Use of included script samples are subject to the terms specified at http://www.microsoft.com/info/cpyright.htm Note: For the benefit of the community-at-large, all responses to this message are best directed to the newsgroup/thread from which they originated. Out of interest, if I use these Disposable types in a windows form, can (or should) I add them to the forms components collection as that automatically has its contents disposed of in the forms own Dispose method? Graham > >The call to the 'Dispose' method is not mandatory. If the GC is about >>to destoy the object, it will be disposed automatically. [quoted text clipped - 22 lines] > Hope that helps > -Chris 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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