Porting C/C++ game logic to Windows Phone 7 - how?

I have mobile phone game cores - by this I mean the pure game logic - (framework independent, i.e. gfx rendering, data loading, user input, sound/music playing is separated), written either开发者_如何学运维 in C or C++ language – the code was running in the past on the Symbian, Windows Mobile 5.x 6.x and Maemo (now MeeGo) . I was thinking of porting some of those games to Windows Phone 7 using the XNA. My question is – do I need to rewrite the core in C# or I can compile to MSIL and use as a DLLs?

Added later:

Check this: Windows Phone 7 and native C++/CLI

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There is no C/C++ compiler for Phone 7. There isn't one for any version of the Compact Framework, in fact, and any "workaround" is likely to generate IL opcodes that are unsupported by the CF.

What this mean, in practicality, is that C/C++ is unusable for anyone working on Phone 7 (except the phone OEMs themselves) and your code will have to be ported to C#.

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Port the games to XNA. Don't port the game engine to .NET, since Windows Phone already have a game engine called XNA.