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ObjectDisposedException and setting dispose object to nothingimplementations I've come across in the web do not do this? Will I overkill my class if I throw the ObjectDisposedException in all of my public methods? Public Sub DoSomething() If Me.disposed Then Throw New ObjectDisposedException() End if End Sub 2) If I've already implement the dispose method, is it necessary to set the object to nothing? Does setting it to nothing help the GC to clean it up sooner? Dim mycls as MyClass ' do something with mycls obj mycls.dipose() mycls = Nothing Thanks! Teressa,
1) It should only be thrown if your method will fail because the object has been disposed. So, a method that does not use any of the resources cleared up in the dispose would not require this. A method that, for example, tries to use the database connection that was closed by Dispose, could throw this exception to indicate the problem. In that scenario however, it might be more accurate to just pass on the exception generated when trying to use the connection. I personally have never used ObjectDisposedException, and have never seen it used either. 2) Setting the object to nothing does help the GC clean up the object sooner. In fact if you never set it to nothing, the object will never be collected. GC can only occur on an object when all references to it are gone. Show quote "Teresa" <Ter***@discussions.microsoft.com> wrote in message news:6F629B1E-4B9A-4AAB-997A-8DE715B9CE33@microsoft.com... > 1) How necessary is it to throw the ObjectDisposedException? I see that > most > implementations I've come across in the web do not do this? Will I > overkill > my class if I throw the ObjectDisposedException in all of my public > methods? > > Public Sub DoSomething() > If Me.disposed Then > Throw New ObjectDisposedException() > End if > End Sub > > 2) If I've already implement the dispose method, is it necessary to set > the > object to nothing? Does setting it to nothing help the GC to clean it up > sooner? > Dim mycls as MyClass > ' do something with mycls obj > mycls.dipose() > mycls = Nothing > > Thanks! Sean Hederman <us***@blogentry.com> wrote:
> 2) Setting the object to nothing does help the GC clean up the object This is simply wrong. For local variables, setting the variable to > sooner. In fact if you never set it to nothing, the object will never be > collected. nothing usually makes no difference at all, as the JIT can tell when it is last read. For instance variables, you only need to set the variable to nothing if you expect the containing object to live longer than the referenced object needs to. > GC can only occur on an object when all references to it are Indeed - but that doesn't require anything to be set to nothing.> gone. Setting variables' values to nothing (you can never set an *object* to nothing) unnecessarily clutters up code, reducing readability. -- Jon Skeet - <sk***@pobox.com> http://www.pobox.com/~skeet If replying to the group, please do not mail me too Hi Jon - I'm not sure I follow you discussion to the "set nothing" topic.
I've acutally tried and succeeded in setting an object to nothing, the watch (in debug mode) showed that the object equals to nothing. So is my last line of code not neccessary? Dim mycls as MyClass ' do something with mycls obj mycls.dipose() mycls = Nothing Show quote "Jon Skeet [C# MVP]" wrote: > Sean Hederman <us***@blogentry.com> wrote: > > 2) Setting the object to nothing does help the GC clean up the object > > sooner. In fact if you never set it to nothing, the object will never be > > collected. > > This is simply wrong. For local variables, setting the variable to > nothing usually makes no difference at all, as the JIT can tell when it > is last read. For instance variables, you only need to set the variable > to nothing if you expect the containing object to live longer than the > referenced object needs to. > > > GC can only occur on an object when all references to it are > > gone. > > Indeed - but that doesn't require anything to be set to nothing. > > Setting variables' values to nothing (you can never set an *object* to > nothing) unnecessarily clutters up code, reducing readability. > > -- > Jon Skeet - <sk***@pobox.com> > http://www.pobox.com/~skeet > If replying to the group, please do not mail me too > Jon's right, sorry for not being clear enough. As he said, the only time you
need to specifically set the reference to nothing is if you want it to be garbage collected before the containing object. As an example, consider a service which every hour or so creates an object which it uses and then discards fairly quickly. It could then make sense to ensure that the object is available for garbage collection after you're finished with it, especially if it's a big object. In such a scenario, you would set the reference to Nothing. However, most objects lifetimes are tied to their parent, and/or their scope. For these, it is not neccesary to set the reference to Nothing, since the child objects will be available for garbage collection once their references go out of scope, or their parent is collected. As Jon noted, references may actually be cleared before they go out of scope, if the JIT figures out that they're not used anymore. So, to answer your specific question, you would only need to consider setting mycls to Nothing if the object that contained it would survive significantly longer than mycls, AND mycls was not going out of scope. Show quote "Teresa" <Ter***@discussions.microsoft.com> wrote in message news:3051B8C5-A7A8-45B1-A23E-55F036604646@microsoft.com... > Hi Jon - I'm not sure I follow you discussion to the "set nothing" topic. > I've acutally tried and succeeded in setting an object to nothing, the > watch > (in debug mode) showed that the object equals to nothing. So is my last > line > of code not neccessary? > > Dim mycls as MyClass > ' do something with mycls obj > mycls.dipose() > mycls = Nothing > > "Jon Skeet [C# MVP]" wrote: > >> Sean Hederman <us***@blogentry.com> wrote: >> > 2) Setting the object to nothing does help the GC clean up the object >> > sooner. In fact if you never set it to nothing, the object will never >> > be >> > collected. >> >> This is simply wrong. For local variables, setting the variable to >> nothing usually makes no difference at all, as the JIT can tell when it >> is last read. For instance variables, you only need to set the variable >> to nothing if you expect the containing object to live longer than the >> referenced object needs to. >> >> > GC can only occur on an object when all references to it are >> > gone. >> >> Indeed - but that doesn't require anything to be set to nothing. >> >> Setting variables' values to nothing (you can never set an *object* to >> nothing) unnecessarily clutters up code, reducing readability. >> >> -- >> Jon Skeet - <sk***@pobox.com> >> http://www.pobox.com/~skeet >> If replying to the group, please do not mail me too >> Hi Teresa
You may find these blog entries helpful: Throwing ObjectDisposedException: http://weblogs.asp.net/clyon/archive/2004/09/23/233464.aspx General Dispose Info: http://weblogs.asp.net/clyon/archive/2004/09/21/232445.aspx Setting objects to Nothing (null): http://weblogs.asp.net/clyon/archive/2004/12/01/273144.aspx Hope that helps -Chris -------------------- Show quote > >1) How necessary is it to throw the ObjectDisposedException? I see that most >implementations I've come across in the web do not do this? Will I overkill >my class if I throw the ObjectDisposedException in all of my public methods? > > Public Sub DoSomething() > If Me.disposed Then > Throw New ObjectDisposedException() > End if > End Sub > >2) If I've already implement the dispose method, is it necessary to set the >object to nothing? Does setting it to nothing help the GC to clean it up >sooner? > Dim mycls as MyClass > ' do something with mycls obj > mycls.dipose() > mycls = Nothing > >Thanks! > -- This 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.  |
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