Using Xamarin.Forms.Behaviors in XAML causes TargetInvocationException in iOS but not in Android - xaml

Question

I'm doing a Xamarin.Forms app and I need to use Behaviors. I have added the Xamarin.Forms.Behaviors package to the project and added a behavior to the XAML of one page, so a command is executed when the selection of a ListView changes:
<b:Interaction.Behaviors>
<b:BehaviorCollection>
<b:EventToCommand Command="{Binding ItemSelectedCommand}" EventName="ItemSelected" />
</b:BehaviorCollection>
</b:Interaction.Behaviors>
This works nice on Android but the same project throws a TargetInvocationException when navigating to the same page under iOS. What could be causing this?

Answer 1

The iOS linker of Xamarin is more aggressive when stripping symbols/types that it thinks aren't used or referenced; and Xamarin.Forms XAML is usually the victim of this process.
There are two options to fix this:
- Change the stripping mode of the linker (right click on the Xamarin.iOS project -> Properties -> iOS Build tab -> Set Linker behavior to Link SDK assemblies only or Don't link). This will ensure the minimal amount of symbols (or none at all) are removed when creating the application package, the downside being that the app size will increment dramatically.
- Create a code file that manually references those types (for example creating instances that aren't used) so they aren't automatically stripped. Libraries like MvvmCross use this approach.
The latter method is the recommended although it has a bit more of work to do. The former one should be used when you are using third party libraries with lots of types that are getting stripped and it would take more work to reference all of them.