Will flex 4 work with flex 3 projects?

I can find a version of开发者_StackOverflow中文版 flex 3 since the release of flex 4. Will flex 4 work with my old project files?

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Yes... it will work. Just import your Flex 3 projects into Flex 4.

http://www.adobe.com/devnet/flex/articles/flexbuilder3_to_flashbuilder4.html