Detecting when sound is muted with the silent switch on iPhone or iPad for .NET & Xamarin. Useful for text-to-speech because it does not work when a device is in silent mode. Based on https://github.com/moshegottlieb/SoundSwitch

mute.caf

SilentSwitch.cs

// since there is no API for checking if the silent mode is on, the trick is to play a 50ms silent system sound
// if it takes just a few milliseconds, it means the sound wasn't allowed to play and the silent mode is on

using System;
using Foundation;
using AudioToolbox;
using System.Threading.Tasks;

public class SilentSwitch
{
    readonly SystemSound _sound;

    public SilentSwitch()
    {
        // download the file from this gist and put it into the Resources directory of your iOS project
        var url = NSBundle.MainBundle.GetUrlForResource("mute", "caf");
        _sound = new SystemSound(url);
        _sound.IsUISound = true;
    }

    public async Task<bool> IsEnabled()
    {
        // using DateTime because Stopwatch is inaccurate in async code
        var startTime = DateTime.Now;

        await _sound.PlaySystemSoundAsync();

        var elapsedTime = DateTime.Now - startTime;

        // on iPhone 8 await takes 160-250ms for 50ms-long `mute.caf` but only 3-8ms when the silent switch is on
        return elapsedTime.TotalMilliseconds < 50;
    }
}