How to find how long my computer is being idle (idle time) on C# desktop

Question

How to find how long my computer is being idle (idle time) on C# Desktop Application

Idle time is the total time a computer or device has been powered on, but has not been used. If a computer or computer device is idle for a set period of time, it may go into a standby mode or power off.

is there any way to get that ?

Answer 1

If with idle you mean time elapsed from last user input (as GetIdleTime() function would do) then you have to use GetlastInputInfo() function (see MSDN ):

In C# you have to P/Invoke it:

[DllImport("user32.dll")]
static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);

[StructLayout(LayoutKind.Sequential)]
struct LASTINPUTINFO {
    public uint cbSize;
    public int dwTime;
}

It'll return number of milliseconds elapsed from system boot of last user input . First thing you need is then system boot time, you have that from Environment.TickCount (number of milliseconds from boot) then:

DateTime bootTime = DateTime.UtcNow.AddMilliseconds(-Environment.TickCount);

Now you can have time of last input:

LASTINPUTINFO lii = new LASTINPUTINFO();
lii.cbSize = (uint)Marshal.SizeOf(typeof(LASTINPUTINFO));
GetLastInputInfo(ref lii);

DateTime lastInputTime = bootTime.AddMilliseconds(lii.dwTime);

Elapsed time will then simply be:

TimeSpan idleTime = DateTime.UtcNow.Subtract(lastInputTime);

Answer 2

Depending on your UI framework (you did not specify), you need to catch the WM_ENTERIDLE message and store the time in which the message is received.

How should you catch this message? These guys will tell you for to do it in winforms.