am probably doing something but can't figure out my problem. Any help would be really appreciated:
I am having a CustomControl called Section. A Section is collapsible and therefore its ControlTemplate contains an Expander. The Expanders IsExpanded-Property is bound to the Section's IsExpanded Property via TemplateBinding.
When setting IsExpanded on a Section the Expander collapses, but using the toggleButton within the Expander appears to break that binding. Probably by setting a local value to the Expander's IsExpanded-Property. Anyways, after changing the Expander state via Mouse the binding breaks and setting the Section's IsExpanded doesn't do anything.
This however does not happen when putting an Expander into a view and binding its IsExpanded-Property to some DP in the View.
Also notworthy: Snoop does not show any Bindings on the Expander's IsExpanded-Property. It only shows the Value-Source is ParentTemplate. As soon as I click the ToggleButton to Change IsExpanded the Value-Source changes to Local (possibly breaking the former Binding?)
Section.cs:
public class Section : Control
{
static Section()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(Section), new FrameworkPropertyMetadata(typeof(Section)));
}
public static readonly DependencyProperty IsExpandedProperty = DependencyProperty.Register(
"IsExpanded", typeof (bool), typeof (Section), new PropertyMetadata(default(bool)));
public bool IsExpanded
{
get { return (bool) GetValue(IsExpandedProperty); }
set { SetValue(IsExpandedProperty, value); }
}
}
Generic.xaml Style:
<Style TargetType="{x:Type local:Section}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type local:Section}">
<Expander Header="Test" IsExpanded="{TemplateBinding IsExpanded}" >
<Rectangle Fill="Aqua" Height="200" Width="200" />
</Expander>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Any ideas?
So I found the answer which is pretty basic knowledge actually:
TemplateBindings are always ONEWAY no matter what the MetaData states...
Using:
IsExpanded="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=IsExpanded}"
fixed my problem...