ShrlAlgoToolkit/WPFluent/Controls/GroupBox/GroupBox.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="pack://application:,,,/WPFluent;component/Resources/Variables.xaml" />
    </ResourceDictionary.MergedDictionaries>
    <Style TargetType="{x:Type GroupBox}" x:Key="DefaultGroupBoxStyle">
        <Setter Property="Foreground" Value="{DynamicResource TextFillColorPrimaryBrush}" />
        <Setter Property="Background" Value="{DynamicResource CardBackgroundFillColorDefaultBrush}" />
        <Setter Property="BorderBrush" Value="{DynamicResource ControlElevationBorderBrush}" />
        <Setter Property="FocusVisualStyle" Value="{DynamicResource DefaultControlFocusVisualStyle}" />
        <Setter Property="Border.CornerRadius" Value="{DynamicResource TopControlCornerRadius}" />
        <Setter Property="Padding" Value="9" />
        <Setter Property="SnapsToDevicePixels" Value="True" />
        <Setter Property="OverridesDefaultStyle" Value="True" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type GroupBox}">
                    <Border
                        Background="{TemplateBinding Background}"
                        BorderBrush="{TemplateBinding BorderBrush}"
                        BorderThickness="1"
                        CornerRadius="{DynamicResource ControlCornerRadius}">
                        <Grid>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto" />
                                <RowDefinition Height="*" />
                            </Grid.RowDefinitions>
                            <Border
                                Background="{DynamicResource CardBackgroundFillColorSecondaryBrush}"
                                CornerRadius="{DynamicResource ControlTopCornerRadius}"
                                Grid.Row="0"
                                Padding="{TemplateBinding Padding}"
                                x:Name="Header_Border">
                                <ContentPresenter
                                    ContentSource="Header"
                                    ContentStringFormat="{TemplateBinding HeaderStringFormat}"
                                    ContentTemplate="{TemplateBinding HeaderTemplate}"
                                    ContentTemplateSelector="{TemplateBinding HeaderTemplateSelector}"
                                    HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                                    RecognizesAccessKey="True"
                                    SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
                            </Border>
                            <ContentPresenter
                                ContentStringFormat="{TemplateBinding ContentStringFormat}"
                                ContentTemplate="{TemplateBinding ContentTemplate}"
                                ContentTemplateSelector="{TemplateBinding ContentTemplateSelector}"
                                Grid.Row="1"
                                Margin="{TemplateBinding Padding}"
                                SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
                        </Grid>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
    <Style
        BasedOn="{StaticResource DefaultGroupBoxStyle}"
        TargetType="{x:Type GroupBox}"
        x:Key="{x:Type GroupBox}" />
</ResourceDictionary>