I need that when the button of the free hands of the headphones is pressed a certain code with c # for android is executed. I need to know how to capture that hands-free event.
Check the "C# for Android" documentation. "C# for Android" may not be looking for the event. (Which is why it's better to write your apps in Java/Kotlin - if Google left out a way of capturing an event [highly doubtful], they'd have it added to the next update before they stopped blushing.)