Stretching the items of a grouped ListView horizontally

Question

I'd like to stretch the items of my listview horizontally, so that the green area (a selected ItemContainer) reaches from the groupheader to the right.

I've tried to set every element i could think of to "HorizontalAlignment="Stretch"" but nothing worked.

Here is my ListView

<ListView
            HorizontalAlignment="Stretch"
            x:Name="AppointmentListView"
            ItemContainerStyle="{StaticResource ListViewItemContainerStyle}"
            ItemsSource="{Binding Source={StaticResource SelectedViewSource}}"
            Grid.Column="1"
            Grid.RowSpan="2">
            <ListView.GroupStyle>
                <GroupStyle>
                    <GroupStyle.HeaderTemplate>
                        <DataTemplate>
                            <Grid Width="200">
                                <TextBlock Text="{Binding Converter={StaticResource DateYearStringConv}, Path=Key}" Foreground="White" FontSize="20" FontWeight="Light" Margin="10, 5, 0, 0"/>
                            </Grid>
                        </DataTemplate>
                    </GroupStyle.HeaderTemplate>
                    <GroupStyle.ContainerStyle>
                        <Style TargetType="GroupItem">
                            <Setter Property="Template">
                                <Setter.Value>
                                    <ControlTemplate TargetType="GroupItem" >
                                        <StackPanel Orientation="Horizontal" Margin="0, 0, 0, 10" HorizontalAlignment="Stretch">
                                            <ContentPresenter Content="{TemplateBinding Content}" />
                                            <ItemsControl x:Name="ItemsControl" ItemsSource="{Binding GroupItems}"/>
                                        </StackPanel>
                                    </ControlTemplate>
                                </Setter.Value>
                            </Setter>
                        </Style>
                    </GroupStyle.ContainerStyle>
                    <GroupStyle.Panel>
                        <ItemsPanelTemplate>
                            <StackPanel Orientation="Vertical" HorizontalAlignment="Stretch"/>
                        </ItemsPanelTemplate>
                    </GroupStyle.Panel>
                </GroupStyle>
            </ListView.GroupStyle>
            <ListView.ItemsPanel>
                <ItemsPanelTemplate>
                    <StackPanel Orientation="Vertical"/>
                </ItemsPanelTemplate>
            </ListView.ItemsPanel>
            <ListView.ItemTemplate>
                <DataTemplate>
                    <Canvas Width="400" Height="60" Background="Transparent">
                        <TextBlock Text="Here goes the content" />
                    </Canvas>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

ItemContainerStyle

<Style x:Key="ListViewItemContainerStyle" TargetType="ListViewItem">
    <Setter Property="HorizontalAlignment" Value="Stretch" />
    <Setter Property="FontFamily" Value="{StaticResource ContentControlThemeFontFamily}"/>
    <Setter Property="FontSize" Value="{StaticResource ControlContentThemeFontSize}"/>
    <Setter Property="Background" Value="Transparent"/>
    <Setter Property="TabNavigation" Value="Local"/>
    <Setter Property="IsHoldingEnabled" Value="True"/>
    <Setter Property="Margin" Value="0,0,0,2"/>
    <Setter Property="HorizontalContentAlignment" Value="Left"/>
    <Setter Property="VerticalContentAlignment" Value="Top"/>
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="ListViewItem">
                <Border x:Name="OuterContainer">
                    <VisualStateManager.VisualStateGroups>
                        <VisualStateGroup x:Name="CommonStates">
                            <VisualState x:Name="Normal"/>
                            <VisualState x:Name="PointerOver">
                                <Storyboard>
                                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PointerOverBorder"/>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(FrameworkElement.Margin)" Storyboard.TargetName="PointerOverBorder">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <Thickness>0</Thickness>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="Pressed">
                                <Storyboard>
                                    <PointerDownThemeAnimation TargetName="ContentContainer"/>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(FrameworkElement.Margin)" Storyboard.TargetName="PointerOverBorder">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <Thickness>0</Thickness>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="PointerOverPressed">
                                <Storyboard>
                                    <PointerDownThemeAnimation TargetName="ContentContainer"/>
                                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PointerOverBorder"/>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(FrameworkElement.Margin)" Storyboard.TargetName="PointerOverBorder">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <Thickness>0</Thickness>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="Disabled">
                                <Storyboard>
                                    <DoubleAnimation Duration="0" To="{StaticResource ListViewItemDisabledThemeOpacity}" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="contentPresenter"/>
                                </Storyboard>
                            </VisualState>
                        </VisualStateGroup>
                        <VisualStateGroup x:Name="FocusStates">
                            <VisualState x:Name="Focused">
                                <Storyboard>
                                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="FocusVisual"/>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="Unfocused"/>
                            <VisualState x:Name="PointerFocused"/>
                        </VisualStateGroup>
                        <VisualStateGroup x:Name="SelectionHintStates">
                            <VisualStateGroup.Transitions>
                                <VisualTransition GeneratedDuration="0:0:0.65" To="NoSelectionHint"/>
                            </VisualStateGroup.Transitions>
                            <VisualState x:Name="VerticalSelectionHint">
                                <Storyboard>
                                    <SwipeHintThemeAnimation ToHorizontalOffset="0" TargetName="SelectionBackground" ToVerticalOffset="15"/>
                                    <SwipeHintThemeAnimation ToHorizontalOffset="0" TargetName="ContentBorder" ToVerticalOffset="15"/>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="HorizontalSelectionHint">
                                <Storyboard>
                                    <SwipeHintThemeAnimation ToHorizontalOffset="-23" TargetName="SelectionBackground" ToVerticalOffset="0"/>
                                    <SwipeHintThemeAnimation ToHorizontalOffset="-23" TargetName="ContentBorder" ToVerticalOffset="0"/>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="NoSelectionHint"/>
                        </VisualStateGroup>
                        <VisualStateGroup x:Name="SelectionStates">
                            <VisualState x:Name="Unselecting"/>
                            <VisualState x:Name="Unselected"/>
                            <VisualState x:Name="UnselectedPointerOver">
                                <Storyboard>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="contentPresenter">
                                        <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ListViewItemSelectedForegroundThemeBrush}"/>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="UnselectedSwiping"/>
                            <VisualState x:Name="Selecting">
                                <Storyboard>
                                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="SelectionBackground"/>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="contentPresenter">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <SolidColorBrush Color="White"/>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(Shape.Fill)" Storyboard.TargetName="SelectionBackground">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <SolidColorBrush Color="#FF82BA00"/>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="Selected">
                                <Storyboard>
                                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="SelectionBackground"/>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="contentPresenter">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <SolidColorBrush Color="White"/>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(Shape.Fill)" Storyboard.TargetName="SelectionBackground">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <SolidColorBrush Color="#FF82BA00"/>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="SelectedSwiping">
                                <Storyboard>
                                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="SelectionBackground"/>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="contentPresenter">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <SolidColorBrush Color="White"/>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(Shape.Fill)" Storyboard.TargetName="SelectionBackground">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <SolidColorBrush Color="#FF82BA00"/>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="SelectedUnfocused">
                                <Storyboard>
                                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="SelectionBackground"/>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="contentPresenter">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <SolidColorBrush Color="White"/>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(Shape.Fill)" Storyboard.TargetName="SelectionBackground">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <SolidColorBrush Color="#FF82BA00"/>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                        </VisualStateGroup>
                        <VisualStateGroup x:Name="DragStates">
                            <VisualStateGroup.Transitions>
                                <VisualTransition GeneratedDuration="0:0:0.2" To="NotDragging"/>
                            </VisualStateGroup.Transitions>
                            <VisualState x:Name="NotDragging"/>
                            <VisualState x:Name="Dragging">
                                <Storyboard>
                                    <DoubleAnimation Duration="0" To="{StaticResource ListViewItemDragThemeOpacity}" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="InnerDragContent"/>
                                    <DragItemThemeAnimation TargetName="InnerDragContent"/>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="DraggingTarget">
                                <Storyboard>
                                    <DropTargetItemThemeAnimation TargetName="OuterContainer"/>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="MultipleDraggingPrimary">
                                <Storyboard>
                                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="MultiArrangeOverlayBackground"/>
                                    <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="MultiArrangeOverlayText"/>
                                    <DoubleAnimation Duration="0" To="{StaticResource ListViewItemDragThemeOpacity}" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="ContentBorder"/>
                                    <FadeInThemeAnimation TargetName="MultiArrangeOverlayBackground"/>
                                    <FadeInThemeAnimation TargetName="MultiArrangeOverlayText"/>
                                    <DragItemThemeAnimation TargetName="ContentBorder"/>
                                    <FadeOutThemeAnimation TargetName="SelectionBackground"/>
                                    <FadeOutThemeAnimation TargetName="PointerOverBorder"/>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="MultipleDraggingSecondary">
                                <Storyboard>
                                    <FadeOutThemeAnimation TargetName="ContentContainer"/>
                                </Storyboard>
                            </VisualState>
                        </VisualStateGroup>
                        <VisualStateGroup x:Name="ReorderHintStates">
                            <VisualStateGroup.Transitions>
                                <VisualTransition GeneratedDuration="0:0:0.2" To="NoReorderHint"/>
                            </VisualStateGroup.Transitions>
                            <VisualState x:Name="NoReorderHint"/>
                            <VisualState x:Name="BottomReorderHint">
                                <Storyboard>
                                    <DragOverThemeAnimation Direction="Bottom" ToOffset="{StaticResource ListViewItemReorderHintThemeOffset}" TargetName="ReorderHintContent"/>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="TopReorderHint">
                                <Storyboard>
                                    <DragOverThemeAnimation Direction="Top" ToOffset="{StaticResource ListViewItemReorderHintThemeOffset}" TargetName="ReorderHintContent"/>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="RightReorderHint">
                                <Storyboard>
                                    <DragOverThemeAnimation Direction="Right" ToOffset="{StaticResource ListViewItemReorderHintThemeOffset}" TargetName="ReorderHintContent"/>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="LeftReorderHint">
                                <Storyboard>
                                    <DragOverThemeAnimation Direction="Left" ToOffset="{StaticResource ListViewItemReorderHintThemeOffset}" TargetName="ReorderHintContent"/>
                                </Storyboard>
                            </VisualState>
                        </VisualStateGroup>
                        <VisualStateGroup x:Name="DataVirtualizationStates">
                            <VisualState x:Name="DataAvailable"/>
                            <VisualState x:Name="DataPlaceholder">
                                <Storyboard>
                                    <ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="PlaceholderTextBlock">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <Visibility>Visible</Visibility>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                    <ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="PlaceholderRect">
                                        <DiscreteObjectKeyFrame KeyTime="0">
                                            <DiscreteObjectKeyFrame.Value>
                                                <Visibility>Visible</Visibility>
                                            </DiscreteObjectKeyFrame.Value>
                                        </DiscreteObjectKeyFrame>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                        </VisualStateGroup>
                    </VisualStateManager.VisualStateGroups>
                    <Grid x:Name="ReorderHintContent">
                        <Border x:Name="ContentContainer">
                            <Grid x:Name="InnerDragContent">
                                <Rectangle x:Name="PointerOverBorder" Fill="{StaticResource ListViewItemPointerOverBackgroundThemeBrush}" IsHitTestVisible="False" Margin="1" Opacity="0"/>
                                <Rectangle x:Name="FocusVisual" IsHitTestVisible="False" Opacity="0" Stroke="{StaticResource ListViewItemFocusBorderThemeBrush}" StrokeThickness="2"/>
                                <Rectangle x:Name="SelectionBackground" Margin="0" Opacity="0"/>
                                <Border x:Name="ContentBorder" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Margin="0">
                                    <Grid>
                                        <ContentPresenter x:Name="contentPresenter" ContentTemplate="{TemplateBinding ContentTemplate}" ContentTransitions="{TemplateBinding ContentTransitions}" Content="{TemplateBinding Content}" Margin="{TemplateBinding Padding}"/>
                                        <TextBlock x:Name="PlaceholderTextBlock" Foreground="{x:Null}" IsHitTestVisible="False" Margin="{TemplateBinding Padding}" Opacity="0" Text="Xg"/>
                                        <Rectangle x:Name="PlaceholderRect" Fill="{StaticResource ListViewItemPlaceholderBackgroundThemeBrush}" IsHitTestVisible="False" Visibility="Collapsed"/>
                                        <Rectangle x:Name="MultiArrangeOverlayBackground" Fill="{StaticResource ListViewItemDragBackgroundThemeBrush}" IsHitTestVisible="False" Opacity="0"/>
                                    </Grid>
                                </Border>
                                <TextBlock x:Name="MultiArrangeOverlayText" Foreground="{StaticResource ListViewItemDragForegroundThemeBrush}" FontSize="26.667" FontFamily="{StaticResource ContentControlThemeFontFamily}" IsHitTestVisible="False" Margin="18,9,0,0" Opacity="0" TextWrapping="Wrap" Text="{Binding TemplateSettings.DragItemsCount, RelativeSource={RelativeSource Mode=TemplatedParent}}" TextTrimming="WordEllipsis"/>
                            </Grid>
                        </Border>
                    </Grid>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

Answer 1

I found the solution!

I had to change the GroupItemTemplate inside the GroupStyle.ContainerStyle to a Grid

<GroupStyle.ContainerStyle>
<Style TargetType="GroupItem">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="GroupItem" >
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="auto" />
                        <ColumnDefinition Width="*" />
                    </Grid.ColumnDefinitions>
                    <ContentPresenter Content="{TemplateBinding Content}" />
                    <ItemsControl Grid.Column="1" x:Name="ItemsControl" ItemsSource="{Binding GroupItems}"/>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

Answer 2

This is what's needed for the header:

<GroupStyle.HeaderContainerStyle>
    <Style TargetType="ListViewHeaderItem">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ListViewHeaderItem">
                    <ContentPresenter Content="{TemplateBinding Content}" HorizontalAlignment="Stretch"/>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</GroupStyle.HeaderContainerStyle>