c# - Why a custom dependency property is not animated by a DoubleAnimation? -

i have following wpf window:

<window x:class="animationtest.mainwindow"     x:name="main"      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     title="mainwindow" height="350" width="525" >  <window.resources>     <storyboard repeatbehavior="forever" x:key="animationstoryboard" targetname="main" targetproperty="currentoffset" >         <doubleanimation from="0" to="100" duration="0:0:5"  speedratio=".8" autoreverse="true" />     </storyboard> </window.resources>  <grid>  </grid> </window> 

with following code behind:

using system.windows; using system.windows.media.animation;  namespace animationtest { public partial class mainwindow : window {     public static dependencyproperty currentoffsetproperty = dependencyproperty.register("currentoffset", typeof(double), typeof(mainwindow), new frameworkpropertymetadata(oncurrentoffsetpropertychanged));      private static void oncurrentoffsetpropertychanged(dependencyobject d, dependencypropertychangedeventargs e)     {         mainwindow control = (mainwindow)d;     }      public double currentoffset     {                 {             return (double)base.getvalue(mainwindow.currentoffsetproperty);         }         set         {             messagebox.show("hit");             base.setvalue(mainwindow.currentoffsetproperty, value);         }     }      public mainwindow()     {         initializecomponent();          ((storyboard)base.findresource("animationstoryboard")).begin(this);     } } } 

i expected have currentoffset property continuosly called nothing happens. it's animation won't start. can point me wrong?

thanks in advance.

adding previous comment , @clemens

just tried code myself , works fine. you'll ofc have "do work" in propertychanged handler dp works expected.

i modified storyboard not repeat test dp value such as:

<storyboard x:key="animationstoryboard"             targetproperty="currentoffset"             targetname="main">   <doubleanimation duration="0:0:5"                     from="0"                     speedratio=".8"                     to="100" /> </storyboard> 

and code-behind:

public mainwindow() {   initializecomponent();   var sb = ((storyboard)base.findresource("animationstoryboard"));   sb.completed += (sender, args) => messagebox.show(currentoffset.tostring());   sb.begin(); } 

messagebox invoked value of 99.8888... looks it's pretty working fine.