title: Can xamarin apps be built for Windows, MacOS with same source code?
body: <p>Given an app written in C# for Xamarin, can it be built to run on all the supported platforms with minimal changes, including Android, iOS, MacOS, Windows?</p>
  
  <p>I realize that Xamarin claims 90% of the code is shareable across platforms (and 10% needs to be customized), and I'm referring to that "90%". </p>
  
  <p><em>What I don't understand is whether that 90% is shareable across the different Xamarin tools,e.g. Xamarin.Forms and Xamarin.Mac or if those are substantially different tools with different APIs, etc.</em></p>
  
  <p>For example, I see that with Xamarin.Forms I can build for iOS, Android, and Windows. But not MacOS. So, on a Mac, can I install Xamarin.Mac and then build the same app for MacOS ?</p>