Can't bind to IsExpanded on Expander

Question

Blacklight is an older set of WPF controls and styles. The code can be found here. It contains a control called AnimatedExpander which isn't really an expander, rather it just implements HeaderedContentControl and adds an IsExpandedProperty dprop:

    public static readonly DependencyProperty IsExpandedProperty =
       DependencyProperty.Register("IsExpanded", typeof(bool), typeof(AnimatedExpander), new PropertyMetadata(true));

    public bool IsExpanded
    {
        get
        {
            if (this.expandToggleButton != null)
            {
                return this.expandToggleButton.IsChecked.Value;
            }

            return (bool)GetValue(IsExpandedProperty);
        }

        set
        {
            SetValue(IsExpandedProperty, value);
        }
    }

I need to bind to IsExpanded so that I can persist whether expanders are expanded. I'm pretty sure I have the binding setup correctly, and that there is a problem with this custom dependency property. If I open the view in Snoop, and set the IsExpanded=True on the expander, the binding works. However, just clicking the expandToggleButton on the control only expands the control, it doesn't hit my binding.

    <controls:AnimatedExpander IsExpanded="{Binding SGGExpanderExpanded}" />

    private bool _sGGExpanderExpanded;
    public bool SGGExpanderExpanded
    {
        get { return _sGGExpanderExpanded; }
        set
        {
            if (_sGGExpanderExpanded != value)
            {
                _sGGExpanderExpanded = value;
                OnPropertyChanged("SGGExpanderExpanded");
            }
        }
    }

How can I bind to a value that changes when the user clicks the toggle button that is wired to expand the control?

Thanks for the interest. The code is available at the link, and can be tested by simply binding one of the example AnimatedExpanders to a dummy viewmodel. As I have the bad solution I mentioned working, I can't afford to waste a bunch of time looking for a good solution right now. I'll try to come back on the weekend to find a pure MVVM solution. — JoeB, Apr 04 '13 at 18:10
right. I'm almost sure that the problem you're having is due to a bad implementation in that control. — Federico Berasategui, Apr 04 '13 at 18:14
Here's the control. I shared above what looked fishy to me (details in a dprop, which I know WPF can ignore). After more research I'm thinking some style is getting in the way. Here are the two files: http://blacklight.codeplex.com/SourceControl/changeset/view/15166#267951 http://blacklight.codeplex.com/SourceControl/changeset/view/15166#267944 — JoeB, Apr 04 '13 at 18:20

score 0 · Accepted Answer · answered Apr 04 '13 at 18:04

0

A bad solution:

I was able to make this work by attaching an event to the ToggleButton click and looking at the "sender" Content and IsChecked values to update my viewmodel.

answered Apr 04 '13 at 18:04

JoeB

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Can't bind to IsExpanded on Expander

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