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very straight forward question. My company has developed a windows phone 7 app and have been testing it on a windows phone 7 device. Can we safely assume that the same app will be backwards compatible and work seamlessly on a windows phone 8 device such as a Nokia Lumia 920?

Thanks in advance!

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Yes it will work. But it won't take advantage of all the WP8 features like a real WP8 app would. I'd suggest that you create a copy of the project and update it to WP8 for a better performence. Also replace any listboxes with LongListSelectors for example.

robertk
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  • That's great news thank you very much. I'm assuming that you can only update the WP7 app in visual studio 2012 and with the WP8 api installed? –  Dec 05 '12 at 14:08
  • Yes you need VS2012 + WP8 SDK to do that. Note that the SDK requires Windows 8 due to the virtual machine requirement. – robertk Dec 05 '12 at 14:13
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    You are welcome :) If you are interested here's a video from the Build conference talking a bit about the performance changes between WP7 and WP8. http://channel9.msdn.com/Events/Build/2012/3-048 – robertk Dec 05 '12 at 16:58
  • At 19min in he shows how much inpact the upgrade has on performance. It's quite big really :) – robertk Dec 05 '12 at 17:06
  • Awesome! That's the main reason we want to port the app to WP8 and drop WP7. The performance is just absolutely terrible on WP7 devices! –  Dec 06 '12 at 09:49
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In most scenarios it should just work, but you should check this list of known breaking changes and you should also test your app on new devices thoroughly, just in case.
For example FMRadio class is no longer working on WP8 and there are other similar issues:
App platform compatibility for Windows Phone

Martin Suchan
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