In-App messages will work by default if you’ve included the Appboy.bundle folder in your application. On Xamarin we don’t currently support In-App message custom styling. If you would like to customize your in-app message UI, please implement the ABKInAppMessageControllerDelegate method
ABKInAppMessageViewController InAppMessageViewControllerWithInAppMessage(ABKInAppMessage inAppMessage); and return your custom view controller. That will make sure Braze passes you the in-app message object rather than displaying it for you. You will then have the option of displaying the in-app message object’s content manually.