Mouse DoubleClick in Silverlight

We are implementing a mouse-doubleclick event in the TimeLine Visualizer control, but that is not native to Silverlight. There are a number of code snippets on the web about how to do this, but I think the implementation of the event is nice enough to share here.

The event fires when the mouse is clicked twice within a certain time, and within a certain distance. I think the spatial/temporal tolerances make for a smooth user experience. The code consists of static variables to store the position and time of last mouse-click, and extension methods to compare the current values to the stored values. The code should be self-explanatory (While we are one the subject, can anybody point me to a good online code formatter for blogger? Live Writer refuses to install on my machine which has Windows 7 Ultimate, 32-bit):

1:      #region Mouse Double Click  
2:      //initialize to 2 secs back, so event doesnt fire very first time user clicks on control  
3:      static DateTime _lastClicked = DateTime.Now.AddSeconds(-2);  
4:      static Point _lastMousePosition = new Point(1, 1);  
5:      private const double MousePositionTolerance = 20;  
6:      public static bool IsDoubleClick(this MouseButtonEventArgs e)  
7:      {  
8:        bool ret = false;  
9:        if ((DateTime.Now.Subtract(_lastClicked) < TimeSpan.FromMilliseconds(500))  
10:          && (e.GetPosition(null).GetDistance(_lastMousePosition) < MousePositionTolerance))  
11:        {  
12:          ret = true;  
13:        }  
14:        _lastClicked = DateTime.Now;  
15:        _lastMousePosition = e.GetPosition(null);  
16:        return ret;  
17:      }  
18:      #endregion  
19:      public static double GetDistance(this Point current, Point other)  
20:      {  
21:        double x = current.X - other.X;  
22:        double y = current.Y - other.Y;  
23:        return Math.Sqrt(x * x + y * y);  
24:      }  

The consumer code will handle the MouseLeftButtonDown event and examine it to see if it is a double-click, like this:

private void HandleMouseLeftButtonDown(object sender, MouseButtonEventArgs e)

{

if (e.IsDoubleClick())

{....

Caveat Emptor:
The calling method should make sure that all code paths execute e.DoubleClick().

Take, for instance, a calling method like this:

if (condition1 == true)
{
condition1 = false;
do something;
}
else if (e.IsDoubleClick())
{
Do what you do on doubleclick;
}

Here IsDoubleClick is not called the first time the Mousedown event happens, so the static variables _lastPosition and _lastClicked are not set. Hence, IsDoubleClick will not return true when a true double-click happens.

Hope this helps.