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WPF GroupStyle only for groups with more than 1 item

I am trying to show different groups in Listview that contain an expander and a title. However, I do not want my SecondLevel group to display the title if the group contains only 1 element. Since it would be inconvenient. My code is:

<Window x:Class="ListViewGrouping.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:listViewGrouping="clr-namespace:ListViewGrouping"
    Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
    <listViewGrouping:GroupItemStyleSelector x:Key="groupItemStyleSelector"/>
    <!-- Style for the first level GroupItem -->
        <Style x:Key="FirstLevel" TargetType="{x:Type GroupItem}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type GroupItem}">
                        <Expander IsExpanded="True">
                            <Expander.Header>
                                <Grid>
                                    <Grid.ColumnDefinitions>
                                        <ColumnDefinition Width="Auto"/>
                                        <ColumnDefinition Width="Auto"/>
                                        <ColumnDefinition Width="Auto"/>
                                    </Grid.ColumnDefinitions>
                                    <TextBlock Grid.Column="0" Margin="3.5,0" Text="{Binding Name}" TextBlock.FontWeight="Bold"/>
                                    <TextBlock Grid.Column="1" Margin="3.5,0" Text="Elements:"/>
                                    <TextBlock Grid.Column="2" Margin="3.5,0" Text="{Binding ItemCount}"/>
                                </Grid>
                            </Expander.Header>
                            <ItemsPresenter />
                        </Expander>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        <!-- Style for the second level GroupItem -->
        <Style x:Key="SecondLevel" TargetType="{x:Type GroupItem}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type GroupItem}">
                        <Expander IsExpanded="True" Margin="15,0,0,0">
                            <Expander.Header>
                                <TextBlock Text="{Binding Name}" TextBlock.FontWeight="Bold"/>
                            </Expander.Header>
                            <ItemsPresenter />
                        </Expander>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>
    <Grid>
        <ListView Name="mailView" ItemsSource="{Binding}">
            <ListView.GroupStyle>
                <GroupStyle ContainerStyleSelector="{StaticResource groupItemStyleSelector}" />
            </ListView.GroupStyle>
            <ListView.View>
                <GridView>
                    <GridViewColumn Header="ID" DisplayMemberBinding="{Binding ID}"/>
                    <GridViewColumn Header="Subject" DisplayMemberBinding="{Binding Subject}"/>
                    <GridViewColumn Header="Sender" DisplayMemberBinding="{Binding Sender}"/>
                    <GridViewColumn Header="Support-ID" DisplayMemberBinding="{Binding Support_ID}"/>
                    <GridViewColumn Header="Supporter" DisplayMemberBinding="{Binding Supporter}"/>
                    <GridViewColumn Header="Received" DisplayMemberBinding="{Binding ReceivedDate}"/>
                </GridView>
            </ListView.View>
        </ListView>
    </Grid>

Code behind:

    private void createMailList()
    {
        _mails.Add(new Mail("LIC", "Lizenz geht nicht", "Xeun", "LIC.2013.01.10.002", "Xeun", "25.09.2013"));
        _mails.Add(new Mail("CD", "Alles doof", "Xeun", "CD.2013.01.10.002", "Xeun", "25.09.2013"));
        _mails.Add(new Mail("CD", "Re:Alles doof", "Xeun", "CD.2013.01.10.002", "Xeun", "25.09.2013"));
        _mails.Add(new Mail("CD", "CD kaputt", "Xeun", "CD.2013.01.10.003", "Xeun", "25.09.2013"));
        _mails.Add(new Mail("CD", "Geht nicht", "Xeun", "CD.2013.01.10.001", "Xeun", "25.09.2013"));
        _mails.Add(new Mail("LIC", "Kaputt", "Xeun", "LIC.2013.01.10.001", "Xeun", "25.09.2013"));
    }
    public MainWindow()
    {

        InitializeComponent();

        createMailList();
        DataContext = _mails;
        ICollectionView view = CollectionViewSource.GetDefaultView(_mails);
        PropertyGroupDescription groupDescription = new PropertyGroupDescription("ID");
        view.GroupDescriptions.Add(groupDescription);
        view.GroupDescriptions.Add(new PropertyGroupDescription("Support_ID"));
    }

}
public class GroupItemStyleSelector : StyleSelector
{
    public override Style SelectStyle(object item, DependencyObject container)
    {
        Style s;

        CollectionViewGroup group = item as CollectionViewGroup;
        Window window = Application.Current.MainWindow;

        if (!group.IsBottomLevel)
        {
            s = window.FindResource("FirstLevel") as Style;
        }
        else
        {
            s = window.FindResource("SecondLevel") as Style;
        }

        return s;
    }
}

I hope I explained my problem quite well - I attached a screenshot of a small application - groups marked as red contain only one element and should not be displayed as a group. screenshot

+4
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2 answers

  • For both styles, the separation of the ControlTemplate is 2, one with an expander and one with a missing one.

  • , ( CollectionViewGroup)

     return yourGroup.Items.Count > 1

  • DataTrigger, , ( DataContext - , Binding = "{Binding}"

xaml:

 <ControlTemplate TargetType="{x:Type GroupItem}" x:Key="withExpander">
     <Expander IsExpanded="True">
         <Expander.Header>
               .....
         </Expander.Header>
         <ItemsPresenter />
      </Expander>
  </ControlTemplate>


  <ControlTemplate TargetType="{x:Type GroupItem}" x:Key="withOutExpander">        
        <ItemsPresenter />          
  </ControlTemplate>

  <Style x:Key="FirstLevel" TargetType="{x:Type GroupItem}">
      <Setter Property="Template" Value="{StaticResource withExpander}" />

      <Style.Triggers>
          <DataTrigger Binding="{Binding , Converter={StaticResource GroupSizeToExpanderConverter}" Value="False">
                  <Setter Property="Template" Value="{StaticResource withOutExpander}"/>
          </DataTrigger>    
      </Style.Triggers>
  </Style>

:

* ( CollectionViewGroup)

:

public class GroupSizeToExpanderConverter: IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        CollectionViewGroup grp = (CollectionViewGroup)value;
        return grp.Items.Count() > 1; // ALTERNATIVLY grp.ItemCount;             
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}
+8

<GroupStyle>
<GroupStyle.ContainerStyle>
    <Style TargetType="{x:Type GroupItem}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate>
                    <Grid>
                        <Expander IsExpanded="True">
                            <Expander.Style>
                                <Style TargetType="Expander">
                                    <Setter Property="Visibility" Value="Visible"></Setter>
                                    <Style.Triggers>
                                        <DataTrigger Binding="{Binding ItemCount}" Value="1">
                                            <Setter Property="Visibility" Value="Collapsed"></Setter>
                                        </DataTrigger>
                                    </Style.Triggers>
                                </Style>
                            </Expander.Style>
                            <Expander.Header>
                                <StackPanel Orientation="Horizontal">
                                    <TextBlock Text="{Binding Name}" FontWeight="Bold" Foreground="Gray" FontSize="22" VerticalAlignment="Bottom" />
                                    <TextBlock Text="{Binding ItemCount}" FontSize="22" Foreground="Green" FontWeight="Bold" FontStyle="Italic" Margin="10,0,0,0" VerticalAlignment="Bottom" />
                                    <TextBlock Text=" item(s)" FontSize="22" Foreground="Silver" FontStyle="Italic" VerticalAlignment="Bottom" />
                                </StackPanel>
                            </Expander.Header>
                            <Border BorderBrush="LightBlue" BorderThickness="2" Margin="0 2">
                                <ItemsPresenter />
                            </Border>
                        </Expander>
                        <ItemsPresenter>
                            <ItemsPresenter.Style>
                                <Style TargetType="ItemsPresenter">
                                    <Setter Property="Visibility" Value="Collapsed"></Setter>
                                    <Style.Triggers>
                                        <DataTrigger Binding="{Binding ItemCount}" Value="1">
                                            <Setter Property="Visibility" Value="Visible"></Setter>
                                        </DataTrigger>
                                    </Style.Triggers>
                                </Style>
                            </ItemsPresenter.Style>
                        </ItemsPresenter>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</GroupStyle.ContainerStyle>

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