How to save the IsExpanded state in group headers of a listview - Take 2

Question

To get some context this question refers to How to save the IsExpanded state in group headers of a listview

What am I missing here?

When I try to do what is suggested in the referenced post I get:

BindingExpression path error: '[]' property not found on 'object' ''ExpandStateManager'

My ExpandStateManager

public class ExpandStateManager
{
    Dictionary<Category, bool> expandStates = new Dictionary<Category, bool>();

    public bool this[Category key]
    {
        get
        {
            if (!expandStates.ContainsKey(key)) return false;
            return expandStates[key];
        }
        set
        {
            expandStates[key] = value;
        }
    }
}

XAML

    <ListView ItemsSource="{Binding Source={StaticResource cvs}}"  ItemTemplate="{StaticResource animalTemplate}"
     Width="200">
        <ListView.GroupStyle>
            <GroupStyle>
                <GroupStyle.ContainerStyle>
                    <Style TargetType="{x:Type GroupItem}">
                        <Setter Property="Template">
                            <Setter.Value>
                                <ControlTemplate TargetType="{x:Type GroupItem}">
                                    <Expander IsExpanded="{Binding Source={StaticResource ExpandStateManger}, Path=[Items[0].ObjectType]}">
                                        <Expander.Header>
                                            <DockPanel>
                                                <TextBlock Text="{Binding Name}" />
                                            </DockPanel>
                                        </Expander.Header>
                                        <Expander.Content>
                                            <ItemsPresenter />
                                        </Expander.Content>
                                    </Expander>
                                </ControlTemplate>
                            </Setter.Value>
                        </Setter>
                    </Style>
                </GroupStyle.ContainerStyle>
            </GroupStyle>
        </ListView.GroupStyle>
    </ListView>

score 5 · Answer 1 · edited May 21 '20 at 02:58

Here is how I solved similar problem:

<ListView  x:Name="listViewOpportunitiesHistory" ItemsSource="{Binding}" AlternationCount="2" 
    IsTextSearchEnabled="False" IsSynchronizedWithCurrentItem="True"   >
    <ListView.GroupStyle>
        <GroupStyle>
            <GroupStyle.ContainerStyle>
                <Style TargetType="{x:Type GroupItem}">
                    <Setter Property="Margin" Value="0,0,0,5"/>
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{x:Type GroupItem}">
                                <Grid x:Name="grid_ControlTemplate_listViewOpportunitiesHistory" 
                                    Loaded="grid_ControlTemplate_listViewOpportunitiesHistory_Loaded">
                                    <Expander  BorderBrush="#FFA4B97F" BorderThickness="0,0,0,1"  
                                        x:Name="expanderControlTemplate" 
                                        Expanded="expanderExpandCollapse_Expanded" 
                                        Collapsed="expanderExpandCollapse_Collapsed" >
                                        <Expander.Header>
                                            <DockPanel>
                                                <TextBlock FontWeight="Bold" Text="{Binding Path=Name}" Margin="5,0" Width="Auto"/>
                                                <TextBlock FontWeight="Bold" Text="{Binding Path=ItemCount}"/>
                                                <TextBlock FontWeight="Bold" Text=" Items"/>
                                            </DockPanel>
                                        </Expander.Header>
                                        <Expander.Content>
                                            <ItemsPresenter />
                                        </Expander.Content>
                                    </Expander>
                                </Grid>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </GroupStyle.ContainerStyle>
        </GroupStyle>
    </ListView.GroupStyle>
    <ListView.View>
        <GridView>
            <GridView.Columns>      
               <GridViewColumn Width="Auto" x:Name="listViewOpportunitiesHistoryColumn_Time"  >
                    <GridViewColumnHeader Click="SortClickHistory" Tag="Time" Content=" Time "
                        x:Name="listViewOpportunitiesHistoryColumnHeader_Time"  />
                    <GridViewColumn.CellTemplate >
                        <DataTemplate>
                            <Border BorderBrush ="Gray" BorderThickness="0,0,1,0" Margin="-6,0,-6,0">
                                <Grid Margin="6,0,6,0" >
                                    <TextBlock Text="{Binding Path=Time, StringFormat='yyyy-MM-dd HH:mm:ss.fff'}" 
                                        Grid.Column ="0" TextTrimming="CharacterEllipsis" 
                                        VerticalAlignment="Center" HorizontalAlignment="Left" 
                                        ToolTipService.ToolTip="{Binding Path=Time}" />
                                </Grid>
                            </Border>
                        </DataTemplate>
                    </GridViewColumn.CellTemplate>
                </GridViewColumn>
               <GridViewColumn Width="Auto" x:Name="listViewOpportunitiesHistoryColumn_AOValue"  >
                    <GridViewColumnHeader Click="SortClickHistory" Tag="AOValue" Content=" AO Value "
                        x:Name="listViewOpportunitiesHistoryColumnHeader_AOValue"  />
                    <GridViewColumn.CellTemplate >
                        <DataTemplate>
                            <Border BorderBrush ="Gray" BorderThickness="0,0,1,0" Margin="-6,0,-6,0">
                                <Grid Margin="6,0,6,0" >
                                    <TextBlock Text="{Binding Path=AOValue}" Grid.Column ="0" TextTrimming="CharacterEllipsis"
                                        VerticalAlignment="Center" HorizontalAlignment="Left" 
                                        ToolTipService.ToolTip="{Binding Path=AOValue}" />
                                </Grid>
                            </Border>
                        </DataTemplate>
                    </GridViewColumn.CellTemplate>
                </GridViewColumn>       
            </GridView.Columns>
        </GridView>
    </ListView.View>  
</ListView>

Code behind:

private Dictionary<string, bool?> expandStates = new Dictionary<string, bool?>();

private void grid_ControlTemplate_listViewOpportunitiesHistory_Loaded(object sender, 
    RoutedEventArgs e)
{
    var grid = (Grid)sender;
    var dc = grid.DataContext as CollectionViewGroup;
    var groupName = (string)dc.Name.ToString();

    //If the dictionary contains the current group, 
    //retrieve a saved state of the group
    if (this.expandStates.ContainsKey(groupName))
    {
        var expander = (Expander)grid.FindName("expanderControlTemplate");
        //btn.IsExpanded = this.expandStates[groupName];
        if (this.expandStates[groupName] == true)
        {
            expander.IsExpanded = true;
        }
        if (this.expandStates[groupName] == false)
        {
            expander.IsExpanded = false;
        }

    }     
}     

private void expanderExpandCollapse_Collapsed(object sender, RoutedEventArgs e)
{
    var expander = (Expander)sender;
    var dc = (CollectionViewGroup)expander.DataContext;
    var groupName = (string)dc.Name.ToString();

    //Loaded event is fired earlier than the Click event, 
    //so I'm sure that the dictionary contains the key
    this.expandStates[groupName] = expander.IsExpanded; //Save the current state
}

private void expanderExpandCollapse_Expanded(object sender, RoutedEventArgs e)
{
    var expander = (Expander)sender;
    var dc = (CollectionViewGroup)expander.DataContext;
    var groupName = (string)dc.Name.ToString();

    //Loaded event is fired earlier than the Click event, 
    //so I'm sure that the dictionary contains the key
    this.expandStates[groupName] = expander.IsExpanded; //Save the current state
}

I get the data from DataSet:

ICollectionView view = CollectionViewSource.GetDefaultView(dataSet.Tables[0]); 
view.GroupDescriptions.Add(new 
    PropertyGroupDescription(FXH.string_GroupBy_OpportunitiesHistory));
     listViewOpportunitiesHistory.ItemsSource = view;

Just remove some unneeded parts of code. My solution is partially based on this StackOverflow question.

This is excellent. Don't know how many hours I've wasted on this before finally finding this post. This solution worked great! — Nik, Feb 08 '18 at 03:23

How to save the IsExpanded state in group headers of a listview - Take 2

1 Answers1