Using SetWaitableTimer in WPF

SetWaitableTimer is a Windows API function that creates a waitable timer object that you can use to schedule a callback function to be called after a specified amount of time. In order to use SetWaitableTimer in a WPF application, you can use P/Invoke to call this function from your C# code.

Here is an example of how to use SetWaitableTimer in a WPF application:

csharpCopy code
using System;

using System.Runtime.InteropServices;

using System.Threading;

using System.Windows;

using System.Windows.Threading;



namespace WpfApp1

{

    public partial class MainWindow : Window

    {

        [DllImport("kernel32.dll", SetLastError = true)]

        static extern IntPtr CreateWaitableTimer(IntPtr lpTimerAttributes, bool bManualReset, string lpTimerName);



        [DllImport("kernel32.dll", SetLastError = true)]

        static extern bool SetWaitableTimer(IntPtr hTimer, [In] ref long pDueTime, int lPeriod, IntPtr pfnCompletionRoutine, IntPtr lpArgToCompletionRoutine, bool fResume);



        private IntPtr _timerHandle;



        public MainWindow()

        {

            InitializeComponent();



            // Create the timer

            _timerHandle = CreateWaitableTimer(IntPtr.Zero, true, "MyWaitableTimer");



            // Schedule the timer to fire after 5 seconds

            long dueTime = -50000000;

            SetWaitableTimer(_timerHandle, ref dueTime, 0, IntPtr.Zero, IntPtr.Zero, true);



            // Set up a callback to be called when the timer fires

            ThreadPool.RegisterWaitForSingleObject(_timerHandle, TimerCallback, null, -1, false);

        }



        private void TimerCallback(object state, bool timedOut)

        {

            // This method will be called when the timer fires

            // It will be called on a separate thread, so we need to use the Dispatcher

            // to update the UI

            Dispatcher.Invoke(() =>

            {

                MessageBox.Show("Timer fired!");

            });

        }

    }

}

In this example, we create the timer using CreateWaitableTimer, and schedule it to fire after 5 seconds using SetWaitableTimer. We then register a callback function to be called when the timer fires using ThreadPool.RegisterWaitForSingleObject.

When the timer fires, the TimerCallback method is called on a separate thread. Since this method modifies the UI, we need to use the Dispatcher to update the UI thread. In this example, we show a message box to indicate that the timer has fired.