c# - Checking the time difference between boolean values -

i've got boolean value called ispressed active when keyboard , mouse buttons active. want achieve when ispressed boolean value true start timer (preferably using stopwatch class). while ispressed true keep timer going , ispressed false stop timer , difference. after it's stopped , it's true again , stops again, add difference previous timer.

i tried use code post couldn't work. tried doing like:

stopwatch stopwatch = new stopwatch(); timespan ts = stopwatch.elapsed; if (ispressed) {     stopwatch.start(); } else {     stopwatch.stop();     string elapsedtime = string.format("{0:00}:{1:00}:{2:00}.{3:00}", ts.hours, ts.minutes, ts.seconds, ts.milliseconds / 10);     lbltime.text = string.format("{0}", elapsedtime); } 

the lbltime label stayed @ 0.

i'm thinking stopwatch maybe unnecessary overhead. mark time ispressed set true , time ispressed set false , calculation.

    private long _pressedticks;     private long _durationticks;      private bool _pressed;      public bool pressed     {         { return _pressed; }         set         {             if (value == _pressed)             {                 //do nothing;             }             else if (value == false)             {                 _durationticks = datetime.now.ticks - _pressedticks;                 _pressed = value;             }             else             {                 _pressed = value;                 _pressedticks = datetime.now.ticks;             }         }     }