I recently had the task to port a .Net mobile application to iOS, with Xamarin.iOS.
The application is not a game, but is based on the MonoGame game engine because it requires a lot of fluidity and some advanced multi-touch interactions with the user. Performances are therefore critical.
Most of the porting was simple and almost straightforward, but I struggled for a few days trying to meet the performance requirements: when idle, the app would behave correctly and be very fluid, but as soon as I was starting to actually use it and triggered some code, the fps dropped dramatically and most of the app was unresponsive for at least a few seconds…
The application was already working pretty well on Android, so I was really not expecting this.
After checking a lot of things in the code and in the Xamarin documentation without finding anything, I finally solved the problem after trying some last resort thing…