<Border CornerRadius="8" BorderThickness="2" BorderBrush="#BF66FF">
    <Border.Background>
        <LinearGradientBrush StartPoint="1,1" EndPoint="0,0">
            <LinearGradientBrush.GradientStops>
                <GradientStop Offset="0.0" Color="#9E01AB"/>
                <GradientStop Offset="0.5" Color="#4A0197"/>
            </LinearGradientBrush.GradientStops>
        </LinearGradientBrush>
    </Border.Background>
</Border>