simple ValueChanged example

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Core;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;

using Windows.Devices.Gpio;

//Szablon elementu Pusta strona jest udokumentowany na stronie https://go.microsoft.com/fwlink/?LinkId=402352&clcid=0x415

namespace valueChangedTest
{
    /// <summary>
    /// Pusta strona, która może być używana samodzielnie lub do której można nawigować wewnątrz ramki.
    /// </summary>
    public sealed partial class MainPage : Page
    {
        // Use GPIO pin 5 to set values
        private const int SET_PIN = 5;
        private GpioPin setPin;

        // Use GPIO pin 6 to listen for value changes
        private const int LISTEN_PIN = 27;
        private GpioPin listenPin;

        private GpioPinValue currentValue = GpioPinValue.High;
        private DispatcherTimer timer;

        public MainPage()
        {
            this.InitializeComponent();
        }

        private void Grid_Loaded(object sender, RoutedEventArgs e)
        {
            // Initialize the GPIO objects.
            var gpio = GpioController.GetDefault();

            // Set up our GPIO pin for setting values.
            // If this next line crashes with a NullReferenceException,
            // then the problem is that there is no GPIO controller on the device.
            setPin = gpio.OpenPin(SET_PIN);

            // Establish initial value and configure pin for output.
            setPin.Write(currentValue);
            setPin.SetDriveMode(GpioPinDriveMode.Output);

            // Set up our GPIO pin for listening for value changes.
            listenPin = gpio.OpenPin(LISTEN_PIN);

            // Configure pin for input and add ValueChanged listener.
            listenPin.SetDriveMode(GpioPinDriveMode.Input);
            listenPin.ValueChanged += Pin_ValueChanged;

            // Start toggling the pin value every 500ms.
            timer = new DispatcherTimer();
            timer.Interval = TimeSpan.FromMilliseconds(500);
            timer.Tick += Timer_Tick;
            timer.Start();
        }

        private void Pin_ValueChanged(GpioPin sender, GpioPinValueChangedEventArgs e)
        {
            // Report the change in pin value.
            var task = Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
            {
                CurrentPinValue.Text = listenPin.Read().ToString();
            });
        }

        private void Timer_Tick(object sender, object e)
        {
            // Toggle the existing pin value.
            currentValue = (currentValue == GpioPinValue.High) ? GpioPinValue.Low : GpioPinValue.High;
            setPin.Write(currentValue);
        }
    }
}