Expand/Collapse all expanders - wpf

Question

I have a list of expanders which I want to control its expanded state(IsExpanded) with global toggle button which should toggle between expanded/collapsed state.
The solution which I have got so far does that by binding the expander's IsExpanded state to the togglebutton's IsChecked state. This works as long as I dont manually dont toggle the expanders. Once I do that those particular expanders dont respect the binding (toggle button's IsChecked state).
Any idea why? and is there a clean solution in XAML for this?
<Page
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Grid>
<StackPanel>
<ToggleButton Name="ExpandAll">Toggle</ToggleButton>
<Expander IsExpanded="{Binding ElementName=ExpandAll,Path=IsChecked, Mode=OneWay}">
Hai
</Expander>
<Expander IsExpanded="{Binding ElementName=ExpandAll,Path=IsChecked, Mode=OneWay}">
Hello
</Expander>
<Expander IsExpanded="{Binding ElementName=ExpandAll,Path=IsChecked, Mode=OneWay}">
Weird
</Expander>
</StackPanel>
</Grid>
</Page>

Answer 1

I know that this post is very old. Just posting this for anyone else who comes across. The below code worked for me.
<Expander IsExpanded="{Binding ElementName=ExpandAll, Path=IsChecked, UpdateSourceTrigger=Explicit}">
</Expander>
This works when the expanders are generated dynamically, for example inside a DataGrid.RowDetailsTemplate.

Answer 2

I don't think you can achieve this entirely in XAML, but the following allows you to do it with an IValueConverter:
<StackPanel>
<StackPanel.Resources>
<local:Converter x:Key="Converter" />
</StackPanel.Resources>
<ToggleButton Name="ExpandAll">
<ToggleButton.IsChecked>
<MultiBinding Mode="OneWayToSource" Converter="{StaticResource Converter}">
<Binding ElementName="Expander1" Path="IsExpanded" />
<Binding ElementName="Expander2" Path="IsExpanded" />
<Binding ElementName="Expander3" Path="IsExpanded" />
</MultiBinding>
</ToggleButton.IsChecked>
Toggle</ToggleButton>
<Expander Name="Expander1">
Hai
</Expander>
<Expander Name="Expander2">
Hello
</Expander>
<Expander Name="Expander3">
Weird
</Expander>
</StackPanel>
And your Converter is as below:
public class Converter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
//we're using OneWayToSource, so this will never be used.
return DependencyProperty.UnsetValue;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
{
// we want to convert the single 'IsChecked' value from the ToggleButton into
// 3 'IsExpanded' values
var allValues = new object[targetTypes.Length];
for (int i = 0; i < allValues.Length; i++)
{
allValues[i] = value;
}
return allValues;
}
}
This works by setting up a OneWayToSource binding between the IsChecked property of the ToggleButton (i.e. the binding will be set against the source when the target value changes), and uses an IMultiValueConverter to translate the single value into one for each of the Expanders.