Disposing of object used in a UserControl...
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Hi Pete, I always have been, and still am, struggling with this question. Here is a simple example: I create a UserControl that holds a PictureBox; I create a modal Form holding two such UserControls and some Buttons Initially the Form loads one image and shows it in both UC. then: scenario 1: I press a button and another image gets loaded in one of the UCs (the original image remains in use in the other UC) scenario 2: I press another button and one UserControl should vanish (the image remains in use in the other UC) scenario 3: I press yet another button, it closes the Form (the image is no longer referenced). So who should be calling Image.Dispose()? It can't be the UC, as it does not "own" the image. It shouldn't be the Form, as it will be very vulnerable as soon as the use cases get a bit complex. So we need some pattern here that automates/hides the problem. FWIW: the problem vanishes if one never assigns the same image to different UCs, which implies each UC shows a different instance of Image (possibly showing the same thing though), but I want to avoid loading the same image twice if I can reliably do so. And I don't see how a WeakReference will help me; I know how to use them to possibly keep an object alive, as in a user-created cache. However here the PictureBoxes want to be sure they have the image at hand that they are supposed to show, nothing is supposed to be weak here. :confused:
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
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Wow, talk about going way beyond the original problem. Right, here are some thoughts based on work we've done with this in the past. If you want to show the same image in multiple locations then you don't make the lifetime of the image the responsibility of the items that are showing it. In other words, I'd have an ImageManager class that contained the image. When the controls want the image, then I would return a clone of that image to the control instead - the control can then happily dispose of that image. The lifetime of the ImageManager is then independent of the user control and can be maintained as a WeakReference. We have used this technique successfully in several projects and it's worked well for us.
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
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Wow, talk about going way beyond the original problem. Right, here are some thoughts based on work we've done with this in the past. If you want to show the same image in multiple locations then you don't make the lifetime of the image the responsibility of the items that are showing it. In other words, I'd have an ImageManager class that contained the image. When the controls want the image, then I would return a clone of that image to the control instead - the control can then happily dispose of that image. The lifetime of the ImageManager is then independent of the user control and can be maintained as a WeakReference. We have used this technique successfully in several projects and it's worked well for us.
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
Yeah, that is what I was afraid of, another Manager. :laugh: Thanks. I was still hoping a ready-made solution existed. Acutally, you now said it can't be the UC's responsibility. That is a change of heart from before[^]. The UC, being a component, is open to reuse.
Pete O'Hanlon wrote:
going way beyond the original problem
curiosity. the ambition to learn. generalization. advancement. you name it. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
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Yeah, that is what I was afraid of, another Manager. :laugh: Thanks. I was still hoping a ready-made solution existed. Acutally, you now said it can't be the UC's responsibility. That is a change of heart from before[^]. The UC, being a component, is open to reuse.
Pete O'Hanlon wrote:
going way beyond the original problem
curiosity. the ambition to learn. generalization. advancement. you name it. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
Luc Pattyn wrote:
another Manager
You can never have enough managers. The UK is proof how well that works. :rolleyes:
Luc Pattyn wrote:
curiosity. the ambition to learn. generalization. advancement. you name it.
Hoo yeah. I'm almost tempted to write a blog post demonstrating this.
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
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Luc Pattyn wrote:
another Manager
You can never have enough managers. The UK is proof how well that works. :rolleyes:
Luc Pattyn wrote:
curiosity. the ambition to learn. generalization. advancement. you name it.
Hoo yeah. I'm almost tempted to write a blog post demonstrating this.
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
Pete O'Hanlon wrote:
I'm almost tempted to write a blog post demonstrating this.
what else do you need? I'll be reading it! :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
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Pete O'Hanlon wrote:
I'm almost tempted to write a blog post demonstrating this.
what else do you need? I'll be reading it! :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
Luc Pattyn wrote:
what else do you need?
Time.
Luc Pattyn wrote:
I'll be reading it!
Ah. A reader. Excellent.
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
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Pete O'Hanlon wrote:
I'm almost tempted to write a blog post demonstrating this.
what else do you need? I'll be reading it! :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
I've posted an article demonstrating a simple weak referenced image library that demonstrates what I've been talking about. It's available here[^].
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
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I've posted an article demonstrating a simple weak referenced image library that demonstrates what I've been talking about. It's available here[^].
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
Hi Pete, thanks for the notification. BTW: you may want to check the downloads, they seem pretty empty at the moment. Regards,
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
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Hi Pete, thanks for the notification. BTW: you may want to check the downloads, they seem pretty empty at the moment. Regards,
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).
What??? Try now - for some reason the article editor put in a borked entry (or two).
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
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Hello experts, I'm currently developing a UserControl in which I have a browseable Image property. What is the correct approach to dispose this image? Should my UserControl dispose of it when it gets disposed? That would create a potential problem if the Image is used elsewhere around the application. But then again, not doing so means taking the chance that the image is not disposed. Thanks in advance, Shy.
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What??? Try now - for some reason the article editor put in a borked entry (or two).
"WPF has many lovers. It's a veritable porn star!" - Josh Smith
As Braveheart once said, "You can take our freedom but you'll never take our Hobnobs!" - Martin Hughes.
All is well now. Thanks. :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
I only read formatted code with indentation, so please use PRE tags for code snippets.
I'm not participating in frackin' Q&A, so if you want my opinion, ask away in a real forum (or on my profile page).