Launched today, the iPhone/iOS to Windows Phone 7 API mapping tool helps developers find their way around when they discover the Windows Phone platform. Think of the API mapping tool as being like a translation dictionary. For example, let's say that you're planning a vacation to France. Since you don't speak the language, you'll bring a pocket travel dictionary. Having this tool will surely help you to get some idea about what you are ordering from a restaurant menu but you'll have no idea what the actual recipe is -- nor will you be able to have a conversion in French with the server! But that's a great learning tool to make the first steps.
With this tool, iPhone developers can grab their apps, pick out the iOS API calls, and quickly look up the equivalent classes, methods and notification events in WP7. A developer can search a given iOS API call and find the equivalent WP7 along with C# sample codes and API documentations for both platforms.
The code samples allow developers to quickly migrate short blobs of iOS code to the equivalent C# code. All WP7 API documentations are pulled in from the Silverlight, C# and XNA sources on MSDN.
For more detail, check http://windowsphone.interoperabilitybridges.com/
Also, check Windows Phone 7 Guide for iPhone Application Developers