#1,163 – Make an Image Clickable with a Control Template

You can allow clicking on an Image by using it as the control template for a Button.

In the example below, we define a button that consists of an image and a border that lights up when you hover over the image.

	<StackPanel>
		<Button Click="Button_Click"
                Margin="10"
			    HorizontalAlignment="Center"
			    ToolTip="Click on Fred">
			<Button.Template>
				<ControlTemplate>
					<Border x:Name="theBorder" 
                            BorderBrush="Transparent"
                            BorderThickness="2">
						<Image Source="Astaire.png" Height="45"/>
					</Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="BorderBrush" TargetName="theBorder" 
                                    Value="LightSkyBlue"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
				</ControlTemplate>
			</Button.Template>
		</Button>
	</StackPanel>

Below, we can see the clickable Image in action.
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#993 – Default Control Template for a ListBox

The default control template used for a ListBox (in version 4.5 of the .NET Framework) is shown below.  The template is included within a style that includes some other default property values.

The core structure of the ListBox is simple–an ItemsPresenter, within a ScrollViewer and surrounded by a Border.

    <Window.Resources>
        <Style x:Key="lbDefaultStyle" TargetType="{x:Type ListBox}">
            <Setter Property="Background" Value="White"/>
            <Setter Property="BorderBrush" Value="#FFABADB3"/>
            <Setter Property="BorderThickness" Value="1"/>
            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
            <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
            <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
            <Setter Property="ScrollViewer.CanContentScroll" Value="True"/>
            <Setter Property="ScrollViewer.PanningMode" Value="Both"/>
            <Setter Property="Stylus.IsFlicksEnabled" Value="False"/>
            <Setter Property="VerticalContentAlignment" Value="Center"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ListBox}">
                        <Border x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="1" SnapsToDevicePixels="True">
                            <ScrollViewer Focusable="False" Padding="{TemplateBinding Padding}">
                                <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                            </ScrollViewer>
                        </Border>
                        <ControlTemplate.Triggers>
                            <Trigger Property="IsEnabled" Value="False">
                                <Setter Property="Background" TargetName="Bd" Value="White"/>
                                <Setter Property="BorderBrush" TargetName="Bd" Value="#FFD9D9D9"/>
                            </Trigger>
                            <MultiTrigger>
                                <MultiTrigger.Conditions>
                                    <Condition Property="IsGrouping" Value="True"/>
                                    <Condition Property="VirtualizingPanel.IsVirtualizingWhenGrouping" Value="False"/>
                                </MultiTrigger.Conditions>
                                <Setter Property="ScrollViewer.CanContentScroll" Value="False"/>
                            </MultiTrigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>

    <StackPanel>
        <ListBox Name="lbActors" Margin="15,5" Width="200" Height="200"
                 ItemsSource="{Binding ActorList}"
                 Style="{DynamicResource lbDefaultStyle}"/>
    </StackPanel>

#178 – A Control Can Have Both a Control Template and A Data Template

A control template dictates a control’s constituent controls, while a data template dictates how bound data will be rendered.  A control can actually have both types of templates at the same time.

In the XAML fragment below, we specify a Label‘s Template property, setting it to a ControlTemplate.  (This is actually the default control template for a Label).

We also specify the label’s ContentTemplate as a DataTemplate.  This template dictates how we’ll render the actual data (content) bound to the Label.

        <Label Name="lblPerson" Content="{Binding}">
            <Label.Template>
                <ControlTemplate TargetType="{x:Type Label}">
                    <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
                        <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Label.Template>
            <Label.ContentTemplate>
                <DataTemplate>
                    <Border BorderThickness="2" BorderBrush="DarkBlue">
                        <StackPanel Orientation="Vertical">
                            <StackPanel Orientation="Horizontal">
                                <Label Content="{Binding Path=FirstName}"/>
                                <Label Content="{Binding Path=LastName}" FontWeight="Bold"/>
                            </StackPanel>
                            <Label Content="{Binding Path=BirthYear}" FontStyle="Italic"/>
                        </StackPanel>
                    </Border>
                </DataTemplate>
            </Label.ContentTemplate>
        </Label>

#177 – A Content Presenter Is a Placeholder for a Content Control’s Content

A content control (ContentControl) in WPF is a control that displays a single piece of content.  The control will have a control template (Template property) that describes the specific visual elements that make up the control.  Somewhere in that control template will be a content presenter (ContentPresenter), which indicates the spot in the control to display the actual content.

You can think of the ContentPresenter as a little pointer that says “put your content here”.

Below is the default control template for a Label control as an example.  The control template includes a ContentPresenter inside a Border.

<ControlTemplate TargetType="{x:Type Label}">
    <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Padding="{TemplateBinding Padding}" SnapsToDevicePixels="true">
        <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
    </Border>
    <ControlTemplate.Triggers>
        <Trigger Property="IsEnabled" Value="false">
            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
        </Trigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

#176 – Two Kinds of Templates

In WPF, there are two different kinds of templatescontrol templates and data templates.

Control templates allow you to exactly specify the visual tree of a control, i.e. its constituent controls.  The example below shows a Button control being constructed out of a Button and two Label controls.

        <Button Name="btnWithTemplate" Content="Recreate Me" Foreground="Blue">
            <Button.Template>
                <ControlTemplate TargetType="{x:Type Button}">
                    <StackPanel Orientation="Horizontal">
                        <Label Content="**" Foreground="{TemplateBinding Foreground}"/>
                        <Button Content="{TemplateBinding Content}" Foreground="{TemplateBinding Foreground}"/>
                        <Label Content="**" Foreground="{TemplateBinding Foreground}"/>
                    </StackPanel>
                </ControlTemplate>
            </Button.Template>
        </Button>

 

Data templates allow you to specify how a bound data object will be mapped to one or more controls.  The example below maps properties of a Person object to several labels.

        <Label Name="lblPerson" Content="{Binding}">
            <Label.ContentTemplate>
                <DataTemplate>
                    <Border BorderThickness="2" BorderBrush="DarkBlue">
                        <StackPanel Orientation="Vertical">
                            <StackPanel Orientation="Horizontal">
                                <Label Content="{Binding Path=FirstName}"/>
                                <Label Content="{Binding Path=LastName}" FontWeight="Bold"/>
                            </StackPanel>
                            <Label Content="{Binding Path=BirthYear}" FontStyle="Italic"/>
                        </StackPanel>
                    </Border>
                </DataTemplate>
            </Label.ContentTemplate>
        </Label>