#1,188 – Using an ItemContainerStyle to Animate Items in an ItemsControl

One common use when defining a new ItemContainerStyle for an ItemsControl is to do something special with either the currently selected item or the item that the mouse is currently over.

We can set property values for the currently selected item or the item that the mouse is over, using triggers and property setters.  You can also use a storyboard to animate a transition to a new property value.

Below, we do two things to animate the item that the mouse is currently over.  (Both are done in the Style used for the ItemContainerStyle).

• Add a Setter for the LayoutTransform, containing a ScaleTransform
• Trigger on IsMouseOver, setting up a storyboard to animate the ScaleX and ScaleY properties of the ScaleTransform

        <Style x:Key="FocusVisual">
            <Setter Property="Control.Template">
                <Setter.Value>
                    <ControlTemplate>
                        <Rectangle Margin="2" SnapsToDevicePixels="true" Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" StrokeThickness="1" StrokeDashArray="1 2"/>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        <SolidColorBrush x:Key="Item.MouseOver.Background" Color="#1F26A0DA"/>
        <SolidColorBrush x:Key="Item.MouseOver.Border" Color="#a826A0Da"/>
        <SolidColorBrush x:Key="Item.SelectedInactive.Background" Color="#3DDADADA"/>
        <SolidColorBrush x:Key="Item.SelectedInactive.Border" Color="#FFDADADA"/>
        <SolidColorBrush x:Key="Item.SelectedActive.Background" Color="#3D26A0DA"/>
        <SolidColorBrush x:Key="Item.SelectedActive.Border" Color="#FF26A0DA"/>

        <Style x:Key="lbDefaultItemContainerStyle" TargetType="{x:Type ListBoxItem}">
            <Setter Property="SnapsToDevicePixels" Value="True"/>
            <Setter Property="Padding" Value="4,1"/>
            <Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
            <Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
            <Setter Property="Background" Value="Transparent"/>
            <Setter Property="BorderBrush" Value="Transparent"/>
            <Setter Property="BorderThickness" Value="1"/>
            <Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
            <Setter Property="LayoutTransform">
                <Setter.Value>
                    <ScaleTransform ScaleX="1" ScaleY="1"/>
                </Setter.Value>
            </Setter>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ListBoxItem}">
                        <Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
                            <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                        </Border>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsMouseOver" Value="True">
                                <Trigger.EnterActions>
                                    <BeginStoryboard>
                                        <Storyboard>
                                            <DoubleAnimation To="1.1" Duration="0:0:0.3"
                                                             Storyboard.TargetProperty="LayoutTransform.(ScaleTransform.ScaleX)"/>
                                            <DoubleAnimation To="1.1" Duration="0:0:0.3"
                                                             Storyboard.TargetProperty="LayoutTransform.(ScaleTransform.ScaleY)"/>
                                        </Storyboard>
                                    </BeginStoryboard>
                                </Trigger.EnterActions>
                                <Trigger.ExitActions>
                                    <BeginStoryboard>
                                        <Storyboard>
                                            <DoubleAnimation To="1" Duration="0:0:0.3"
                                                             Storyboard.TargetProperty="LayoutTransform.(ScaleTransform.ScaleX)"/>
                                            <DoubleAnimation To="1" Duration="0:0:0.3"
                                                             Storyboard.TargetProperty="LayoutTransform.(ScaleTransform.ScaleY)"/>
                                        </Storyboard>
                                    </BeginStoryboard>
                                </Trigger.ExitActions>
                                <Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.MouseOver.Background}"/>
                                <Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.MouseOver.Border}"/>
                            </Trigger>
                            <MultiTrigger>
                                <MultiTrigger.Conditions>
                                    <Condition Property="Selector.IsSelectionActive" Value="False"/>
                                    <Condition Property="IsSelected" Value="True"/>
                                </MultiTrigger.Conditions>
                                <Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.SelectedInactive.Background}"/>
                                <Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.SelectedInactive.Border}"/>
                            </MultiTrigger>
                            <MultiTrigger>
                                <MultiTrigger.Conditions>
                                    <Condition Property="Selector.IsSelectionActive" Value="True"/>
                                    <Condition Property="IsSelected" Value="True"/>
                                </MultiTrigger.Conditions>
                                <Setter Property="Background" TargetName="Bd" Value="{StaticResource Item.SelectedActive.Background}"/>
                                <Setter Property="BorderBrush" TargetName="Bd" Value="{StaticResource Item.SelectedActive.Border}"/>
                            </MultiTrigger>
                            <Trigger Property="IsEnabled" Value="False">
                                <Setter Property="TextElement.Foreground" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>