CODEWITHSUNDEEP
c#sendkeys
Oh hi Mark
Oh hi Mark

Reputation: 203

Unpredictable results using sendkeys with capslock

I would like to simulate a user input to prevent the screen from locking. 

public Form1()
{
   aTimer = new System.Threading.Timer(OnTimedEvent, null, 5000, Timeout.Infinite);
}

private void OnTimedEvent(Object source)
{
    Stopwatch watch = new Stopwatch();
    watch.Start();

    if (IdleTimeFinder.GetIdleTime() > 2000) 
    {
        SendKeys.SendWait({CAPSLOCK}); 
    }
    aTimer.Change(Math.Max(0, 5000 - watch.ElapsedMilliseconds), Timeout.Infinite);
 }

My problem is that sometimes capslock stays on or off other times it blinks. It's not very predicable.

Upvotes: 1

Views: 413

Answers (1)

user700390
user700390

Reputation: 2339

I think you may have a race condition between multiple threads giving you inconsistent results.

The correct way to prevent the computer from sleeping is to use the SetThreadExecutionState function.

https://msdn.microsoft.com/en-us/library/windows/desktop/aa373208%28v=vs.85%29.aspx

You can p/Invoke this one pretty easily, I have used it from C# in the past.

To call it from C# you will want to use the following declarations:

http://www.pinvoke.net/default.aspx/kernel32.setthreadexecutionstate

[DllImport("kernel32.dll", CharSet = CharSet.Auto,SetLastError = true)]
static extern EXECUTION_STATE SetThreadExecutionState(EXECUTION_STATE esFlags);

[FlagsAttribute]
public enum EXECUTION_STATE :uint
{
     ES_AWAYMODE_REQUIRED = 0x00000040,
     ES_CONTINUOUS = 0x80000000,
     ES_DISPLAY_REQUIRED = 0x00000002,
     ES_SYSTEM_REQUIRED = 0x00000001
     // Legacy flag, should not be used.
     // ES_USER_PRESENT = 0x00000004
}

Upvotes: 3

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