JackPrescenceWatcher.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
using Windows.Devices.Enumeration;
using Windows.Media.Devices;

namespace HeadphoneJackDetection
{
    public sealed class JackPrescenceEventArgs : EventArgs
    {
        public bool IsPresent { get; set; }
    }

    public delegate void JackPresenceChangedEventHandler(object sender, JackPrescenceEventArgs args);

    public sealed class JackPrescenceWatcher
    {
        private const string AudioEndpointFormFactorProperty = "{1da5d803-d492-4edd-8c23-e0c0ffee7f0e} 0";
        private static readonly string[] props = new string[] {
            AudioEndpointFormFactorProperty, //"PKEY_AudioEndpoint_FormFactor",
        };

        private Windows.Devices.Enumeration.DeviceWatcher watcher;

        public JackPrescenceWatcher()
        {
            //var selector = MediaDevice.GetAudioRenderSelector();
            var selector = "System.Devices.InterfaceClassGuid:=\"{e6327cad-dcec-4949-ae8a-991e976a79d2}\"";
            watcher = DeviceInformation.CreateWatcher(selector, props);
            watcher.Added += HandleDeviceAdded;
            watcher.Updated += HandleDeviceUpdated;
            watcher.Removed += HandleDeviceRemoved;
        }

        /// <summary>
        /// Start watching for insertion or removal
        /// </summary>
        public void Start()
        {
            watcher.Start();
        }

        /// <summary>
        /// Stop watching for insertion or removal
        /// </summary>
        public void Stop()
        {
            watcher.Stop();
        }

        /// <summary>
        /// Raised when an insertion or removal is deteced from the headphone jack.
        /// </summary>
        public event JackPresenceChangedEventHandler JackPresenceChanged;

        private void OnJackPresenceChanged(bool isPresent)
        {
            if (null != this.JackPresenceChanged)
            {
                this.JackPresenceChanged(this, new JackPrescenceEventArgs { IsPresent = isPresent });
            }
        }

        private async void HandleDeviceUpdated(DeviceWatcher sender, DeviceInformationUpdate args)
        {
            var info = await Windows.Devices.Enumeration.DeviceInformation.CreateFromIdAsync(args.Id, props);
            OnDeviceChanged(args.Id, info);
        }

        private void HandleDeviceAdded(Windows.Devices.Enumeration.DeviceWatcher sender, Windows.Devices.Enumeration.DeviceInformation args)
        {
            OnDeviceChanged(args.Id, args);
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="args"></param>
        /// <remarks>
        /// may need to watch for known devices getting physically removed from the system. In that case
        /// info will be null and we'll only have id to know it was removed. May need to keep a cache 
        /// of known deviceId's to watch for physical removal of one we care about. Unlikely scenario for 
        /// the whole headphone jack to be removed, but possible.
        /// </remarks>
        async void HandleDeviceRemoved(DeviceWatcher sender, DeviceInformationUpdate args)
        {
            var info = await Windows.Devices.Enumeration.DeviceInformation.CreateFromIdAsync(args.Id, props);
            OnDeviceChanged(args.Id, info);
        }

        private void OnDeviceChanged(string deviceId, DeviceInformation info)
        {
            object temp;
            if (null != info)
            {
                if (info.Properties.TryGetValue(AudioEndpointFormFactorProperty, out temp))
                {
                    AudioEndpointFormFactor ff = (AudioEndpointFormFactor)Convert.ToInt32(temp);
                    if (ff == AudioEndpointFormFactor.Headphones || ff == AudioEndpointFormFactor.Headset)
                    {
                        if (info.Properties.TryGetValue("System.Devices.InterfaceEnabled", out temp))
                        {
                            bool isInserted = (bool)temp;
                            OnJackPresenceChanged(isInserted);
                        }
                    }
                }
            }
        }

        private enum AudioEndpointFormFactor
        {
            RemoteNetworkDevice = 0,
            Speakers = 1,
            LineLevel = 2,
            Headphones = 3,
            Microphone = 4,
            Headset = 5,
            Handset = 6,
            UnknownDigitalPassthrough = 7,
            SPDIF = 8,
            DigitalAudioDisplayDeviceHDMI = 9,
            UnknownFormFactor = 10
        }
    }
}