ELK/FrameworkLocal/UICore/Style/NavyBlue/GroupBoxStyle.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:converters="clr-namespace:Aitex.Core.UI.Converters">

    <Style TargetType="GroupBox">
        <Setter Property="FontSize" Value="20" />
        <Setter Property="BorderBrush" Value="Black" />
    </Style>



    <converters:CenterBorderGapMaskConverter x:Key="BorderGapMaskConverter"/>


    <Style x:Key="GroupboxWithoutWhiteBorder" TargetType="{x:Type GroupBox}">
        <Setter Property="BorderBrush" Value="#D5DFE5" />
        <Setter Property="BorderThickness" Value="1" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type GroupBox}">
                    <Grid SnapsToDevicePixels="true">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="6" />
                            <ColumnDefinition Width="Auto" />
                            <ColumnDefinition Width="*" />
                            <ColumnDefinition Width="6" />
                        </Grid.ColumnDefinitions>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="Auto" />
                            <RowDefinition Height="Auto" />
                            <RowDefinition Height="*" />
                            <RowDefinition Height="6" />
                        </Grid.RowDefinitions>
                        <Border CornerRadius="4" Grid.Row="1" Grid.RowSpan="3" Grid.Column="0" Grid.ColumnSpan="4" BorderThickness="{TemplateBinding BorderThickness}" BorderBrush="Transparent" Background="{TemplateBinding Background}" />
                        <Border Name="Header" Padding="3,1,3,0" Grid.Row="0" Grid.RowSpan="2" Grid.Column="1">
                            <ContentPresenter ContentSource="Header" RecognizesAccessKey="true" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
                        </Border>
                        <ContentPresenter Grid.Row="2" Grid.Column="1" Grid.ColumnSpan="2" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
                        <Border Grid.Row="1" Grid.RowSpan="3" Grid.ColumnSpan="4"  BorderThickness="{TemplateBinding BorderThickness}" BorderBrush="{TemplateBinding BorderBrush}" CornerRadius="3">
                            <Border.OpacityMask>
                                <MultiBinding Converter="{StaticResource BorderGapMaskConverter}" ConverterParameter="7">
                                    <Binding ElementName="Header" Path="ActualWidth" />
                                    <Binding Path="ActualWidth" RelativeSource="{RelativeSource Self}" />
                                    <Binding Path="ActualHeight" RelativeSource="{RelativeSource Self}" />
                                </MultiBinding>
                            </Border.OpacityMask>
                        </Border>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>


    <Style  x:Key="GroupboxWithoutWhiteBorder2" TargetType="{x:Type GroupBox}">
        <Setter Property="BorderBrush" Value="#D5DFE5"/>
        <Setter Property="BorderThickness" Value="1"/>
        <Setter Property="FontSize" Value="20" />
        <Setter Property="Foreground" Value="White"></Setter>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type GroupBox}">
                    <Grid SnapsToDevicePixels="true">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="6"/>
                            <ColumnDefinition Width="Auto"/>
                            <ColumnDefinition Width="*"/>
                            <ColumnDefinition Width="6"/>
                        </Grid.ColumnDefinitions>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="Auto"/>
                            <RowDefinition Height="Auto"/>
                            <RowDefinition Height="*"/>
                            <RowDefinition Height="6"/>
                        </Grid.RowDefinitions>
                        <Border BorderBrush="Transparent" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.ColumnSpan="4" Grid.Column="0" CornerRadius="4" Grid.Row="1" Grid.RowSpan="3"/>
                        <Border Grid.ZIndex="2" x:Name="Header" Grid.Column="2" HorizontalAlignment="Center" Padding="3,1,3,0" Grid.Row="0" Grid.RowSpan="2">
                            <ContentPresenter ContentSource="Header" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                        </Border>
                        <ContentPresenter Grid.ColumnSpan="2" Grid.Column="1" Margin="{TemplateBinding Padding}" Grid.Row="2" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
                        <Border  BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Grid.ColumnSpan="4" CornerRadius="3" Grid.Row="1" Grid.RowSpan="3">
                            <Border.OpacityMask>
                                <MultiBinding ConverterParameter="7" Converter="{StaticResource BorderGapMaskConverter}">
                                    <Binding ElementName="Header" Path="ActualWidth"/>
                                    <Binding Path="ActualWidth" RelativeSource="{RelativeSource Self}"/>
                                    <Binding Path="ActualHeight" RelativeSource="{RelativeSource Self}"/>
                                </MultiBinding>
                            </Border.OpacityMask>
                            <!--<Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="3">
                                <Border BorderBrush="White" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="2"/>
                            </Border>-->
                        </Border>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>