WPF Expand specific Expander inside Listview

Question

I have a listview in which's groupstyle, i have defined an expander(code below), i programmatically add many items to the listview which get added to the appropriate expander and if the expander does not exist fo the new item, it gets created dynamically.

<ListView.GroupStyle>
                <GroupStyle>
                    <GroupStyle.ContainerStyle>
                        <Style TargetType="{x:Type GroupItem}">
                            <Setter Property="Template">
                                <Setter.Value>
                                    <ControlTemplate TargetType="{x:Type GroupItem}">
                                        <Expander IsExpanded="True" >
                                            <Expander.Header>
                                                <DockPanel>
                                                    <TextBlock FontWeight="Bold" Text="{Binding Path=Name}" Margin="5,0,0,0" Width="100"/>
                                                </DockPanel>
                                            </Expander.Header>
                                            <Expander.Content>
                                                <ItemsPresenter />
                                            </Expander.Content>
                                        </Expander>
                                    </ControlTemplate>
                                </Setter.Value>
                            </Setter>
                        </Style>
                    </GroupStyle.ContainerStyle>
                </GroupStyle>
            </ListView.GroupStyle>

So what needs to be done is that when a new item is added, the focus should divert to that item and the expander should be expanded while collapsing all else...

Answer 1

Use a binding to see if the lists SelectedItem is part of the Group that we are bound to.

<Expander IsExpanded="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=ListView, AncestorLevel=1}, Path=SelectedItem, Converter={StaticResource yourConverter}, ConverterParameter={Binding}}" >

You will Bind IsExpanded to the lists SelectedItem, with a converter parameter that is bound to the viewmodel and have the converter simply check to see if the arguments match.

The converter simply returns true or false

public class yourConvertor : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return ((GroupItem)parameter).Contains(value);
    }
 }

Answer 2

I wanted to expand on the previous answer -- I am using this in an MVVM scenario, and was getting the same error as Billy mentioned above

" A 'Binding' cannot be set on the 'ConverterParameter' property of type 'Binding'. A 'Binding' can only be set on a DependencyProperty of a DependencyObject."

I ended up modifying the converter and XAML as so (the DataContext.CurrentItem is a placeholder for whatever is needed to reference the current item in the View Model):

public class MultiBindingItemsEqualConverter : IMultiValueConverter
{
    #region IMultiValueConverter Members

    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        bool valuesEquals = values[0].Equals(values[1]);
        return valuesEquals;
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }

    #endregion
}

<Expander ...>
    <Expander.IsExpanded>
        <MultiBinding
            Mode="OneWay"
            Converter="{StaticResource MultiBindingItemsEqualConv}">
            <Binding
                RelativeSource="{RelativeSource FindAncestor, AncestorType=ListView, AncestorLevel=1}"
                Path="SelectedItem"></Binding>
            <Binding
                RelativeSource="{RelativeSource FindAncestor, AncestorType=ListView, AncestorLevel=1}"
                Path="DataContext.CurrentItem"></Binding>
        </MultiBinding>
    </Expander.IsExpanded>
</Expander>