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I'd like the background of my CheckBox to change colour depending on if it matches a pre-defined bool (not just if it's Checked or Unchecked). The problem is that this looks poor if you do it to the CheckBox alone, so I've wrapped the CheckBox in a Grid and set the background of the Grid instead. My issue now is that I want to pull out this style so I can reuse it for my other Checkbox

Here is my XAML:

<Grid Margin="5 10 0 0">
    <CheckBox Name="cbJimbo" Content="JIMBO" FontSize="12"
    IsChecked="{Binding MyObject.Jimbo}"                                                                
    Style="{StaticResource CheckBoxStyle}"/>
    <Grid.Style>
        <Style TargetType="Grid">
            <Style.Triggers>
                <DataTrigger Binding="{Binding ElementName=cbJimbo, Path=Background}" Value="Yellow">
                    <Setter Property="Background" Value="Yellow" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </Grid.Style>
</Grid>

What is the best way to refactor this?

In the interest of completeness (Although not entirely relevant) here is the CheckBox style, which determines if the CheckBox matches the default value and then sets the CheckBox background in a too subtle fashion. Also relevant as my Grid is currently bound to the background of this Checkbox:

<Style x:Key="ValidationCheckBox" TargetType="CheckBox" BasedOn="{StaticResource {x:Type CheckBox}}">
    <Setter Property="Validation.ErrorTemplate">
        <Setter.Value>
            <ControlTemplate>
                <StackPanel>
                    <AdornedElementPlaceholder x:Name="placeholder"/>
                </StackPanel>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
    <Style.Triggers>
        <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self},
        Path=(Validation.Errors)/ErrorContent.ErrorType}" Value="{x:Static wrapper:ErrorTypeEnum.Default}">
            <Setter Property="Background" Value="Yellow"/>
        </DataTrigger>
    </Style.Triggers>
</Style>
thatguy
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jimbo
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1 Answers1

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Making Your Style Reusable

If you want create a separate style for the Grid, the element name binding is problematic, since the same name might already exist in this namescope. An alternative, although not very robust is to explicitly specify the child that the CheckBox is via index. It is advisible to trigger on the real property that triggers the CheckBox, too, so you do not have to change the brush to in both style. It also makes the reason for the color change apparent.

<Style TargetType="Grid">
   <Style.Triggers>
      <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Children[0].(CheckBox.Background)}" Value="Yellow">
         <Setter Property="Background" Value="Yellow" />
      </DataTrigger>
   </Style.Triggers>
</Style>

Changing the Control Template

As you might know, the visual appearance and states of a control are defined in a ControlTemplate. Instead of building a Grid around the CheckBox, you could extract its default styleand control template and adapt it, so that it has the same backgroud as the check mark box. There is already a Grid as template root, but its background is set to Transparent. If we replace that with a TemplateBinding to the Background property, it looks as expected.

<Grid x:Name="templateRoot" Background="{TemplateBinding Background}" SnapsToDevicePixels="True">

This is the whole and adapted control template for CheckBox.

<Style x:Key="FocusVisual">
   <Setter Property="Control.Template">
      <Setter.Value>
         <ControlTemplate>
            <Rectangle Margin="2" StrokeDashArray="1 2" Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" SnapsToDevicePixels="true" StrokeThickness="1"/>
         </ControlTemplate>
      </Setter.Value>
   </Setter>
</Style>
<Style x:Key="OptionMarkFocusVisual">
   <Setter Property="Control.Template">
      <Setter.Value>
         <ControlTemplate>
            <Rectangle Margin="14,0,0,0" StrokeDashArray="1 2" Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" SnapsToDevicePixels="true" StrokeThickness="1"/>
         </ControlTemplate>
      </Setter.Value>
   </Setter>
</Style>
<SolidColorBrush x:Key="OptionMark.Static.Background" Color="#FFFFFFFF"/>
<SolidColorBrush x:Key="OptionMark.Static.Border" Color="#FF707070"/>
<SolidColorBrush x:Key="OptionMark.Static.Glyph" Color="#FF212121"/>
<SolidColorBrush x:Key="OptionMark.MouseOver.Background" Color="#FFF3F9FF"/>
<SolidColorBrush x:Key="OptionMark.MouseOver.Border" Color="#FF5593FF"/>
<SolidColorBrush x:Key="OptionMark.MouseOver.Glyph" Color="#FF212121"/>
<SolidColorBrush x:Key="OptionMark.Pressed.Background" Color="#FFD9ECFF"/>
<SolidColorBrush x:Key="OptionMark.Pressed.Border" Color="#FF3C77DD"/>
<SolidColorBrush x:Key="OptionMark.Pressed.Glyph" Color="#FF212121"/>
<SolidColorBrush x:Key="OptionMark.Disabled.Background" Color="#FFE6E6E6"/>
<SolidColorBrush x:Key="OptionMark.Disabled.Border" Color="#FFBCBCBC"/>
<SolidColorBrush x:Key="OptionMark.Disabled.Glyph" Color="#FF707070"/>
<Style x:Key="CheckBoxStyle" TargetType="{x:Type CheckBox}">
   <Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
   <Setter Property="Background" Value="{StaticResource OptionMark.Static.Background}"/>
   <Setter Property="BorderBrush" Value="{StaticResource OptionMark.Static.Border}"/>
   <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
   <Setter Property="BorderThickness" Value="1"/>
   <Setter Property="Template">
      <Setter.Value>
         <ControlTemplate TargetType="{x:Type CheckBox}">
            <Grid x:Name="templateRoot" Background="{TemplateBinding Background}" SnapsToDevicePixels="True">
               <Grid.ColumnDefinitions>
                  <ColumnDefinition Width="Auto"/>
                  <ColumnDefinition Width="*"/>
               </Grid.ColumnDefinitions>
               <Border x:Name="checkBoxBorder" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="1" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
                  <Grid x:Name="markGrid">
                     <Path x:Name="optionMark" Data="F1 M 9.97498,1.22334L 4.6983,9.09834L 4.52164,9.09834L 0,5.19331L 1.27664,3.52165L 4.255,6.08833L 8.33331,1.52588e-005L 9.97498,1.22334 Z " Fill="{StaticResource OptionMark.Static.Glyph}" Margin="1" Opacity="0" Stretch="None"/>
                     <Rectangle x:Name="indeterminateMark" Fill="{StaticResource OptionMark.Static.Glyph}" Margin="2" Opacity="0"/>
                  </Grid>
               </Border>
               <ContentPresenter x:Name="contentPresenter" Grid.Column="1" Focusable="False" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
            </Grid>
            <ControlTemplate.Triggers>
               <Trigger Property="HasContent" Value="true">
                  <Setter Property="FocusVisualStyle" Value="{StaticResource OptionMarkFocusVisual}"/>
                  <Setter Property="Padding" Value="4,-1,0,0"/>
               </Trigger>
               <Trigger Property="IsMouseOver" Value="true">
                  <Setter Property="Background" TargetName="checkBoxBorder" Value="{StaticResource OptionMark.MouseOver.Background}"/>
                  <Setter Property="BorderBrush" TargetName="checkBoxBorder" Value="{StaticResource OptionMark.MouseOver.Border}"/>
                  <Setter Property="Fill" TargetName="optionMark" Value="{StaticResource OptionMark.MouseOver.Glyph}"/>
                  <Setter Property="Fill" TargetName="indeterminateMark" Value="{StaticResource OptionMark.MouseOver.Glyph}"/>
               </Trigger>
               <Trigger Property="IsEnabled" Value="false">
                  <Setter Property="Background" TargetName="checkBoxBorder" Value="{StaticResource OptionMark.Disabled.Background}"/>
                  <Setter Property="BorderBrush" TargetName="checkBoxBorder" Value="{StaticResource OptionMark.Disabled.Border}"/>
                  <Setter Property="Fill" TargetName="optionMark" Value="{StaticResource OptionMark.Disabled.Glyph}"/>
                  <Setter Property="Fill" TargetName="indeterminateMark" Value="{StaticResource OptionMark.Disabled.Glyph}"/>
               </Trigger>
               <Trigger Property="IsPressed" Value="true">
                  <Setter Property="Background" TargetName="checkBoxBorder" Value="{StaticResource OptionMark.Pressed.Background}"/>
                  <Setter Property="BorderBrush" TargetName="checkBoxBorder" Value="{StaticResource OptionMark.Pressed.Border}"/>
                  <Setter Property="Fill" TargetName="optionMark" Value="{StaticResource OptionMark.Pressed.Glyph}"/>
                  <Setter Property="Fill" TargetName="indeterminateMark" Value="{StaticResource OptionMark.Pressed.Glyph}"/>
               </Trigger>
               <Trigger Property="IsChecked" Value="true">
                  <Setter Property="Opacity" TargetName="optionMark" Value="1"/>
                  <Setter Property="Opacity" TargetName="indeterminateMark" Value="0"/>
               </Trigger>
               <Trigger Property="IsChecked" Value="{x:Null}">
                  <Setter Property="Opacity" TargetName="optionMark" Value="0"/>
                  <Setter Property="Opacity" TargetName="indeterminateMark" Value="1"/>
               </Trigger>
            </ControlTemplate.Triggers>
         </ControlTemplate>
      </Setter.Value>
   </Setter>
</Style>

Creating Custom Controls

If you intend to use the same control hierarchy in the same way in multiple places, the original style will not save you from lots of code duplication that makes your code less maintainable. In such scenarios, consider creating a UserControl which encapsulates the control as single, reusable control instead.

The simplest way to create a control in WPF is to derive from UserControl. When you build a control that inherits from UserControl, you add existing components to the UserControl, name the components, and reference event handlers in WPF.

If built correctly, a UserControl can take advantage of the benefits of rich content, styles, and triggers. However, if your control inherits from UserControl, people who use your control will not be able to use a DataTemplate or ControlTemplate to customize its appearance.

If your control is not only a composition of other controls, but a fully-fledged new control with custom behavior and control template as well as theming support, you would create a custom control instead. For more information and differences refer to Control authoring overview.

thatguy
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