Windows Mobile Programming Tricks on the .NET Compact Framework: Part 1

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace BeeMobile
{
    /// <summary>
    /// Represents a functionality which periodically resets the idle timers which measure how
    /// long the user has been idle and subsequently turn the display off.
    /// </summary>
    /// <remarks>
    /// This is useful when writing applications which require the display to be constantly lit.
    /// </remarks>
    public class ResetIdleTimer
    {
#region WIN32
        [DllImport("coredll.dll")]
        private static extern void SystemIdleTimerReset();

        [DllImport("Aygshell.dll")]
        private static extern void SHIdleTimerReset();

        [DllImport("coredll.dll")]
        private static extern int SetSystemPowerState(string pwrState, int pwrStateFlags, int options);

        private const int POWER_STATE_ON = 0x10000;
        private const int POWER_STATE_OFF = 0x20000;
        private const int POWER_STATE_SUSPEND = 0x200000;
        private const int POWER_FORCE = 4096;
#endregion WIN32

        #region " Data members "

        private Timer m_Timer;

        #endregion " Data members "



        #region Constructor
        /// <summary>
        /// Constructs a new ResetIdleTimer object with default 500 ms timer refresh interval.
        /// </summary>
        public ResetIdleTimer()
            : this(500)
        {
        }

        /// <summary>
        /// Constructs a new ResetIdleTimer object.
        /// </summary>
        /// <param name="milisec">Specifies how often the timers should be reset.</param>
        public ResetIdleTimer(int milisec)
        {
            m_Timer = new Timer();
            m_Timer.Interval = milisec; // in milliseconds
            m_Timer.Tick += new EventHandler(Timer_Tick);
        }
        #endregion constructor

        #region Public methods

        /// <summary>
        /// Turns on the display and resets the idle timers.
        /// </summary>
        public static void ResetTimer()
        {
            SetSystemPowerState(null, POWER_STATE_ON, POWER_FORCE);
            SystemIdleTimerReset();
            SHIdleTimerReset();
        }

        /// <summary>
        /// Turns the backlight off.
        /// </summary>
        public static void TurnOffBackLight()
        {
            SetSystemPowerState(null, POWER_STATE_OFF, POWER_FORCE);
        }

        /// <summary>
        /// Call this method to keep the display lit.
        /// </summary>
        public void StartTimer()
        {
            m_Timer.Enabled = true;
        }

        /// <summary>
        /// Call this method to turn off the functionality provided by this class.
        /// </summary>
        public void StopTimer()
        {
            m_Timer.Enabled = false;
        }

        #endregion Public methods

        #region Public properties

        /// <summary>
        /// Gets a value indicating whether the ResetIdleTimer is in effect.
        /// </summary>
        public bool TimerEnabled
        {
            get{
                return this.m_Timer.Enabled;
            }
        }

        /// <summary>
        /// Gets or sets a value indicating how often (in miliseconds) the timer should be rese.t
        /// </summary>
        public int TimerInterval
        {
            get
            {
                return this.m_Timer.Interval;
            }
            set{
                this.m_Timer.Interval = value;
            }
        }

        #endregion Public properties

        private void Timer_Tick(object sender, EventArgs e)
        {
           ResetTimer();
        }

        
    }

}