C# - Detect time of last user interaction with the OS

GetLastInputInfo. Documented at PInvoke.net.

include following namespaces

using System;
using System.Runtime.InteropServices;

and then include following

internal struct LASTINPUTINFO
{
public uint cbSize;


public uint dwTime;
}


/// <summary>
/// Helps to find the idle time, (in milliseconds) spent since the last user input
/// </summary>
public class IdleTimeFinder
{
[DllImport("User32.dll")]
private static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);


[DllImport("Kernel32.dll")]
private static extern uint GetLastError();


public static uint GetIdleTime()
{
LASTINPUTINFO lastInPut = new LASTINPUTINFO();
lastInPut.cbSize = (uint)System.Runtime.InteropServices.Marshal.SizeOf(lastInPut);
GetLastInputInfo(ref lastInPut);


return ((uint)Environment.TickCount - lastInPut.dwTime);
}
/// <summary>
/// Get the Last input time in milliseconds
/// </summary>
/// <returns></returns>
public static long GetLastInputTime()
{
LASTINPUTINFO lastInPut = new LASTINPUTINFO();
lastInPut.cbSize = (uint)System.Runtime.InteropServices.Marshal.SizeOf(lastInPut);
if (!GetLastInputInfo(ref lastInPut))
{
throw new Exception(GetLastError().ToString());
}
return lastInPut.dwTime;
}
}

To convert the tickcount into time you can use

TimeSpan timespent = TimeSpan.FromMilliseconds(ticks);

Note. This routine uses the term TickCount but the values are in milliseconds and are so not the same as Ticks.

From MSDN article on Environment.TickCount

Gets the number of milliseconds elapsed since the system started.

Code:

 using System;
using System.Runtime.InteropServices;


public static int IdleTime() //In seconds
{
LASTINPUTINFO lastinputinfo = new LASTINPUTINFO();
lastinputinfo.cbSize = Marshal.SizeOf(lastinputinfo);
GetLastInputInfo(ref lastinputinfo);
return (((Environment.TickCount & int.MaxValue) - (lastinputinfo.dwTime & int.MaxValue)) & int.MaxValue) / 1000;
}