Windows Form or WPF, to code or not code

I am planning to develop a UI control suite (open source) on .net because there is hardly such things as free 开发者_开发知识库or open source out in the market. But I am not really able to decide the following factors before going into design phase:

1. Should I write it for Winforms only?
2. Should I write it for WPF only?
3. Or, should I write it for both?

Which one would be more effort effective in the long run and help the community better? Can you guys please help me to sort this things out?

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'Writing it for both' is basically 'write it twice', as I can't imagine much would be shared.

I think if I was suddenly filled with the idea that the world needed yet more 3rd party controls, I would write them for WPF/Silverlight/WP7.

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WPF, but it's just my opinion. Windows OSs that are supported (XP, Vista, 7) all support it, and WPF is the future. I don't see Winforms' death in the proximity, but we should support things that are right now actively supported.

It's like developing for IE6 instead of Firefox/Safari/Chrome/Opera. Most of us don't see IE6 dying, but we have to move forward.