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.NET Forum / .NET Framework / General / February 2007How to remove event handler
I'm working in WPF and c# and am adding an event handler to an object like this: this.tgt.SizeChanged += new SizeChangedEventHandler(OnTargetSizeChanged); Later I kill the instance of tgt like this: tgt = null;; //which I'm not sure this is the most correct way of getting rid of it. However, I find that the event 'OnTargetSizeChanged' is still fireing. Evedently the event handler is still alive and wired. Before I kill the object 'tgt', should I be removing any attached event handlers? If so, how? Thanks. moondaddy@noemail.noemail > I'm working in WPF and c# and am adding an event handler to an object like > this: [quoted text clipped - 5 lines] > tgt = null;; //which I'm not sure this is the most correct way of getting > rid of it. That's not "killing" anything. It's making the object available to the garbage collector *if* nothing else is referencing it. Is it still a control on the form, perhaps? > However, I find that the event 'OnTargetSizeChanged' is still fireing. > Evedently the event handler is still alive and wired. Before I kill the > object 'tgt', should I be removing any attached event handlers? If > so, how? Well, I think you need to seriously consider how you're "removing" tgt, but to remove the event handler, just do: this.tgt.SizeChanged -= new SizeChangedEventHandler (OnTargetSizeChanged);  SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too Wouldn't that fail due to the SizeChangedEventHandler being a different instance than was added via +=? > Wouldn't that fail due to the SizeChangedEventHandler being a different > instance than was added via +=? No. They'd still compare as being equal, which is what's used. SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too Well, cool! I was gonna do the -= on some code a while back but saw the new instance I had to create and didn't even check to see if it would work. Guess I can finally fix that! Thanks this looks like just what I need. By the way, this code is running in a class that manages some custom bindings and tgt is a reference to a user control on a canvas. when I connect a line to tgt, I use a custom binding in this class. When tgt becomes un-connected I unbind it from the line and no longer need a reference to tgt so I set tgt=null in the binding management class. However, tgt is still alive and well in the canvas. Saying all of this, is it appropriate to set tgt to null here? or should I do something else? >> I'm working in WPF and c# and am adding an event handler to an object >> like [quoted text clipped - 22 lines] > this.tgt.SizeChanged -= new SizeChangedEventHandler > (OnTargetSizeChanged); > Thanks this looks like just what I need. By the way, this code is running > in a class that manages some custom bindings and tgt is a reference to a [quoted text clipped - 4 lines] > Saying all of this, is it appropriate to set tgt to null here? or should I > do something else? If you want the user control to actually "die" you'll need to remove it from the canvas too. If you just want to not reference it any more from tgt, then setting tgt to null is entirely appropriate. SignatureJon Skeet - <skeet@pobox.com> http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet If replying to the group, please do not mail me too >> Thanks this looks like just what I need. By the way, this code is >> running [quoted text clipped - 12 lines] > from the canvas too. If you just want to not reference it any more from > tgt, then setting tgt to null is entirely appropriate. Great! Thanks alot. >> Thanks this looks like just what I need. By the way, this code is >> running [quoted text clipped - 12 lines] > from the canvas too. If you just want to not reference it any more from > tgt, then setting tgt to null is entirely appropriate. 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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