c# - DispatcherTimer will increasing Interval for every time it's used -

i followed example head first c# on dispatchertimer.

first time press button ticker increase 1 second, next time click on button ticker increase 2 seconds every second/tick. third time ticker increases 3 seconds , on (1 second added every button press).

why , how "reset" ticker interval increase 1 second every time?

here code:

dispatchertimer timer = new dispatchertimer();     private void button_click_1(object sender, routedeventargs e)     {         timer.tick += timer_tick;         timer.interval = timespan.frommilliseconds(1000);         timer.start();         checkhappiness();     }     int = 0;     void timer_tick(object sender, object e)     {         ticker.text = "tick #" + i++;     }      private async void checkhappiness()     {         ... code ..         timer.stop();     }    }   } 

cheers!

timer.tick += timer_tick; 

this line adds method eventhandler everytime press button; in i++ increases one. when have 2 methods doing @ same time (since timer ticks on interval) increase 2 every tick of timer.