XAML Storyboard causing infinite loop. Attempting to animate Progressbar - xaml

Question

Need some help understanding XAML Storyboard animations. I'm attempting to create a countdown animation in a XAML Storyboard using a ProgressBar control. The animation should cause the progress bar to count down from it's maximum value to it's minimum value over a given duration. Here is the relevant XAML:
<ProgressBar x:Name="PollCountdown" Orientation="Vertical" Width="20" Value="{Binding PollValue}" Maximum="{Binding PollMax}" Minimum="{Binding PollMin}" ValueChanged="ProgressBar_ValueChanged">
<ProgressBar.Triggers>
<EventTrigger RoutedEvent="ProgressBar.ValueChanged">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetName="PollCountdown" Storyboard.TargetProperty="Value"
From="{Binding PollMax}" To="{Binding PollMin}" Duration="{Binding Interval, Converter={StaticResource IntToDurationCovnerter}}">
</DoubleAnimation>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</ProgressBar.Triggers>
</ProgressBar>
...and here is the code for the for the ProgressBar_ValueChanged event. The purpose of this is just to allow me to view how the value is changing, and will eventually be removed from the XAML code:
private void ProgressBar_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
{
var x = (sender as ProgressBar).Value;
if (x == 0)
e.Handled = true;
}
Unfortunately, something is causing an infinite loop error to occur when I trigger the animation. By capturing the value_changed event I'm able to monitor the changes in the Value property. What I see occurring is the bar's value decreases by 0.0041 on the first change, but then on the next change, resets back to the bar's Maximum property. Any clues as to what could be causing this infinite loop?

Answer 1

Here is the solution I ultimately came up with. The progressbar will begin/end the countdown with the Run property is set to true/false. The Duration property determines how long the countdown will take.
<ctrl:CountdownBar x:Name="Countdown" Orientation="Vertical" Run="{Binding RunPoll}" VerticalAlignment="Top" Height="121" Margin="0,1,0,-6" Grid.RowSpan="2" HorizontalAlignment="Left" Width="10" >
<ctrl:CountdownBar.Triggers>
<EventTrigger RoutedEvent="ctrl:CountdownBar.Restarting">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetName="Countdown" Storyboard.TargetProperty="Value" Duration="{Binding PollDuration}" From="100" To="0">
</DoubleAnimation>
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</ctrl:CountdownBar.Triggers>
</ctrl:CountdownBar>
And the CountdownBar Control:
public class CountdownBar : ProgressBar
{
public static DependencyProperty IsRunningProperty = DependencyProperty.Register("IsRunning", typeof(bool), typeof(CountdownBar), new PropertyMetadata(false));
public static DependencyProperty DurationProperty = DependencyProperty.Register("Duration", typeof(Duration), typeof(CountdownBar), new PropertyMetadata(new Duration(TimeSpan.FromSeconds(10))));
public static DependencyProperty RunProperty = DependencyProperty.Register("Run", typeof(bool), typeof(CountdownBar), new PropertyMetadata(false));
public static RoutedEvent RestartCountdownEvent = EventManager.RegisterRoutedEvent("Restarting", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(CountdownBar));
public CountdownBar()
{
this.Maximum = 100;
this.Minimum = 0;
this.Value = 100;
this.ValueChanged += Bar_ValueChanged;
}
~CountdownBar()
{
this.ValueChanged -= Bar_ValueChanged;
}
public bool Run
{
get { return ((bool)GetValue(RunProperty)); }
set
{
if (value)
Start();
else
Stop();
SetValue(RunProperty, value);
}
}
public bool IsRunning
{
get { return ((bool)GetValue(IsRunningProperty)); }
set { SetValue(IsRunningProperty, value); }
}
public Duration Duration
{
get { return ((Duration)GetValue(DurationProperty)); }
set { SetValue(DurationProperty, value); }
}
public void Start()
{
IsRunning = true;
this.Value = this.Minimum;
if (Value == 0)
RaiseRestartCountdown();
}
public void Stop()
{
IsRunning = false;
this.Value = this.Maximum;
}
public event RoutedEventHandler Restarting
{
add { AddHandler(RestartCountdownEvent, value); }
remove { RemoveHandler(RestartCountdownEvent, value); }
}
public void RaiseRestartCountdown()
{
RoutedEventArgs args = new RoutedEventArgs(RestartCountdownEvent);
RaiseEvent(args);
}
private void Bar_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
{
if (IsRunning)
if (this.Value == this.Minimum)
if (this.Maximum > this.Minimum)
RaiseRestartCountdown();
}
}
Originally I wanted to make this a completely lookless control, but sometimes you just have to go with what works. If anyone has any ideas to eliminate the c# code and move everything to XAML, please upload a solution.