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Getting the user idle time with C#

, 10 Mar 2006
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Getting the user idle time using C# and the Windows API.

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System idle time is the time that has passed since the computer has received its last input from the user. It can be used to detect whether the user is idle or not. This feature is present in many instant messaging systems.

Visual Studio 2003 does not provide an explicit way to accomplish this, but I found an alternate method using C# code only.

Using the code

The implemented solution calls functions inside the user32.dll and kernel32.dll files.

To do this, it is necessary:

  1. To add a reference to the System.Runtime.InteropServices namespace.
  2. To know the name and definition of the function to be called.
  3. To create an extern function using C#.
  4. To make any additional structure to be used in the called functions.
// Step 1
using System.Runtime.InteropServices;

// Steps 2 and 3
private static extern bool 
        GetLastInputInfo(ref LASTINPUTINFO plii);

//Step 4
internal struct LASTINPUTINFO 
    public uint cbSize;

    public uint dwTime;

When I was trying to make things works, I found an issue with the LASTINPUTINFO structure. I solved the problem by creating a C# struct with the same members as the original function. Note that you need to know the mapping between a Windows data type and the .NET Framework data types. The following table is very useful:

BOOL Boolean variable (should be TRUE or FALSE).
BOOLEAN Boolean variable (should be TRUE or FALSE).
BYTE Byte (8 bits).
CALLBACK Calling convention for callback functions.
CHAR 8-bit Windows (ANSI) character.
COLORREF Red, green, blue (RGB) color value (32 bits).
CONST Variable whose value is to remain constant during execution.
DWORD 32-bit unsigned integer.
DWORD_PTR Unsigned long type for pointer precision. Use when casting a pointer to a long type to perform pointer arithmetic. (Also commonly used for general 32-bit parameters that have been extended to 64 bits in 64-bit Windows.)
INT 32-bit signed integer.
INT_PTR Signed integral type for pointer precision. Use when casting a pointer to an integer to perform pointer arithmetic.
INT32 32-bit signed integer.
INT64 64-bit signed integer.
LONG 32-bit signed integer.
LONG_PTR Signed long type for pointer precision. Use when casting a pointer to a long to perform pointer arithmetic.
LONG32 32-bit signed integer.
LONG64 64-bit signed integer.
LONGLONG 64-bit signed integer.
LPARAM Message parameter.
LPBOOL Pointer to a BOOL.
LPBYTE Pointer to a BYTE.

When using a struct as a parameter, you have to initialize it before it is passed to the function:

lastInPut.cbSize = (uint)

The rest of the code does not contain any trick.

Using the code

The best method to use the code is compiling it in an DLL and using the functions asynchronously using a timer or threads.


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Web Developer
Costa Rica Costa Rica
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Comments and Discussions

GeneralMy vote of 5 PinmemberMember 856175414-Aug-14 3:17 
SuggestionGetLastInputInfo additional info Pinmemberjorge_toriz16-Jun-14 8:39 
BugBUG FOUND & FIXED: Environment.TickCount returns negative value in GetIdleTime() Windows 7 X64 [modified] Pinmemberjeffsdjfhj321-Jun-13 4:01 
GeneralRe: BUG FOUND & FIXED: Environment.TickCount returns negative value in GetIdleTime() Windows 7 X64 [modified] Pinmembersihirbazz10-Jun-14 9:58 
GeneralMy vote of 4 PinmemberJorge Ali Urbina16-Mar-13 8:36 
GeneralMy vote of 5 PinmemberSupriya Srivastav11-Jan-12 22:50 
Nice Article...
GeneralMy vote of 5 Pinmemberandoniu1-Nov-11 22:53 
QuestionWorking in 64 bit Windows Pinmembereduardo zola24-Jul-11 16:28 
GeneralMy vote of 5 PinmemberThat's Aragon21-Jul-11 3:47 
Generalthx Pinmemberbinabic6-May-11 11:49 
GeneralMy vote of 5 PinmemberGilberto Alexandre17-Feb-11 0:33 
QuestionIs it possible in Web forms? Pinmemberdeja_anbu12-Feb-11 23:31 
GeneralBehave really bad on vista PinmemberSergejack27-Jan-10 6:17 
GeneralRe: Behave really bad on vista Pinmembertiuk3-Jun-10 7:33 
GeneralGetting the idle time of another system in network PinmemberSHRIDHAR TL14-Oct-09 3:37 
GeneralRe: Getting the idle time of another system in network PinmemberAndrew Orange17-Dec-09 19:56 
GeneralPretty slick PinmemberMythos724-Aug-09 10:29 
GeneralVirtual machine Issues Pinmembersnorkie16-Apr-09 13:07 
AnswerThis little piece of code saved me this morning PinmemberGerman Sosa11-Apr-09 5:35 
GeneralFantastic Pinmemberz00z07-Oct-08 8:04 
Generalwell done Pinmemberalexandru robert, agrapine7-Jun-08 0:16 
Generalabsolutely great! PinmemberLuis Miguel Silva16-Feb-08 13:46 
GeneralLicense PinmemberGreg Campbell9-Jan-08 13:20 
QuestionGetIdleTime Pinmembersegusmitha25-Sep-07 3:13 
AnswerRe: GetIdleTime PinmemberXavi23cr25-Sep-07 4:08 
GeneralBless you! PinmemberBoaz Cohen19-Aug-07 11:40 
QuestionTotal idle time? Pinmemberid10t7-Feb-07 10:28 
QuestionHave I misundertood the whole thing? Pinmemberpalei13-Dec-06 3:43 
AnswerRe: Have I misundertood the whole thing? Pinmembertiuk3-Jun-10 7:34 
Generalapplication inactivity PinmemberHiggs9619-Sep-06 7:55 
GeneralApplication Idle PinmemberdaDude14-Mar-06 8:31 
GeneralRe: Application Idle PinmemberdaDude14-Mar-06 8:33 
GeneralRe: Application Idle Pinmembermwdiablo18-Apr-06 11:46 
GeneralRe: Application Idle PinmemberdaDude18-Apr-06 15:54 
GeneralApplication Idle PinmemberdaDude14-Mar-06 8:31 
QuestionMouse and keyboard? PinmemberDrew Noakes14-Mar-06 7:31 
AnswerRe: Mouse and keyboard? PinmemberXavi23cr14-Mar-06 10:09 
GeneralOnly Windows 2000 and later PinmemberMarqs13-Mar-06 23:10 
Generalvery useful Pinmemberxsummerx12-Mar-06 0:21 

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