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SilverlightTipoftheDay#82–HowtoImplementDoubleClick

Silverlightcurrentlyhasfullmousesupportforsingleclick.However,doubleclickisaanotherstory.InthistipIwillshowyouhowtoimplementdoubleclick.Youcanapplythistechniqueforanindividualcontrolorevenyourentirepage.

ThekeythingtodoistostartaDispatcherTimertimeroncealeftmouseclickeventhasbeenreceived.Ifanothermouseclickisinterceptedbeforethedoubleclicktimeintervalhaspassedthenadoubleclickhasoccurred.
Thisintervalistypicallysettobearound200milliseconds.Once200millisecondshaspassedthetimerisstoppedanddisableduntilanothermouseclickisreceived.

Tostart,let’screateourtimerandaddalistenerforthe
MouseLeftButtonDownevent.

DispatcherTimer_doubleClickTimer;

Image_lastImage=null;

publicPage()

{

InitializeComponent();

_doubleClickTimer=newDispatcherTimer();

_doubleClickTimer.Interval=newTimeSpan(0,0,0,0,200);

_doubleClickTimer.Tick+=newEventHandler(DoubleClick_Timer);

this.MouseLeftButtonDown+=newMouseButtonEventHandler(Page_MouseLeftButtonDown);

}

//toomuchtimehaspassedforittobeadoubleclick.

voidDoubleClick_Timer(objectsender,EventArgse)

{

_doubleClickTimer.Stop();

}

Now,inthePage_MouseLeftButtonDown()methodwe:

Checkifthetimerisenabled.
Ifitisenabledalready,thenwehavealreadyclickedonceandhavemadeadoubleclick.

Ifisitnotenabledstartthetimer.

voidPage_MouseLeftButtonDown(objectsender,MouseButtonEventArgse)

{

if(_doubleClickTimer.IsEnabled)

{

//adoubleclickhasoccured

_doubleClickTimer.Stop();

ImagecatImg=newImage();

Uriuri=newUri("cat.png",UriKind.Relative);

ImageSourceimgSource=new

System.Windows.Media.Imaging.BitmapImage(uri);

catImg.Source=imgSource;

catImg.SetValue(Canvas.LeftProperty,(double)e.GetPosition(LayoutRoot).X-90);

catImg.SetValue(Canvas.TopProperty,(double)e.GetPosition(LayoutRoot).Y-113);

if(null!=_lastImage)

MainCanvas.Children.Remove(_lastImage);

MainCanvas.Children.Add(catImg);

_lastImage=catImg;

}

else

{

_doubleClickTimer.Start();

}

}