Question

I want to have a slider that returns to 0 when the user stops dragging.

So far I have this:

<Window x:Class="CenteredSliderTest.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="MainWindow" Height="350" Width="525">
<DockPanel>
    <!--Value="{Binding ZSpeed}"-->
    <Slider DockPanel.Dock="Left"
                                x:Name="ZSlider"
                                Minimum="-100" Maximum="100"
                                SelectionStart="-20" SelectionEnd="20"
                                Orientation="Vertical" 
                                TickFrequency="10" 
                                TickPlacement="TopLeft" 
                                AutoToolTipPlacement="TopLeft"
                                AutoToolTipPrecision="2"
                                LargeChange="10"
                                SmallChange="1"
                                IsDirectionReversed="True"
                                Focusable="False"
                                >
        <Slider.Triggers>
            <EventTrigger RoutedEvent="LostMouseCapture" SourceName="ZSlider">
                <EventTrigger.Actions>
                    <BeginStoryboard>
                        <Storyboard>
                            <DoubleAnimation
                                Storyboard.TargetName="ZSlider"
                                Storyboard.TargetProperty="Value"
                                From="{Binding Value, ElementName=ZSlider}"
                                To="0.0"
                                Duration="0:0:1.5"
                                FillBehavior="Stop"
                                />
                        </Storyboard>
                    </BeginStoryboard>
                </EventTrigger.Actions>

            </EventTrigger>
        </Slider.Triggers>
    </Slider>
    <TextBlock Text="{Binding ZSpeed}" />
</DockPanel>
</Window>

This works as long as I don’t bind the slider value to my DependencyProperty ZSpeed.

As soon as I do this, the slider jumps back to the original value and at the second attempt the slider can’t be dragged anymore.

So what can I do (preferable in xaml) in order to get the animation modify not only the slider but also the ZSpeed property?

EDIT

Code in MainWindow:

    public partial class MainWindow : Window
{


    public double ZSpeed
    {
        get { return (double)GetValue(ZSpeedProperty); }
        set { SetValue(ZSpeedProperty, value); }
    }

    // Using a DependencyProperty as the backing store for ZSpeed.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty ZSpeedProperty =
        DependencyProperty.Register("ZSpeed", typeof(double), typeof(MainWindow), new UIPropertyMetadata(0.0));



    public MainWindow()
    {
        InitializeComponent();
        this.DataContext = this;

        Binding binding = new Binding("Value") { Source = ZSlider }; 
        this.SetBinding(ZSpeedProperty, binding); 
    }

}

Answer 1

You might reverse the direction of the binding. Instead of binding the Slider’s Value to ZSpeed you could bind ZSpeed to Value. This would also be the “natural” binding direction if the Slider is meant to change ZSpeed, but ZSpeed won’t change otherwise.

EDIT: If ZSpeed is a dependency property in some data class MyData you could create a binding in code like this:

MyData dataObject = ...
Binding binding = new Binding("Value") { Source = ZSlider };
dataObject.SetBinding(MyData.ZSpeedProperty, binding);

SECOND EDIT: Picking up Daniels suggestion, you might animate ZSpeed instead of the Slider’s Value. Bind the Value to ZSpeed as before, remove the EventTrigger and add an event handler for LostMouseCapture:

<Slider x:Name="ZSlider" ...
        Value="{Binding ZSpeed}"
        LostMouseCapture="ZSlider_LostMouseCapture"/>

Code behind:

private void ZSlider_LostMouseCapture(object sender, MouseEventArgs e)
{
    DoubleAnimation animation = new DoubleAnimation
    {
        From = ZSpeed,
        To = 0d,
        Duration = TimeSpan.FromSeconds(1.5 * Math.Abs(ZSpeed) / 100d),
        FillBehavior = FillBehavior.Stop
    };
    ZSpeed = 0d;
    BeginAnimation(ZSpeedProperty, animation);
}