C# WPF - Black Line in window

Question

In my window threre is small black line. Why?

<Window x:Class="WpfPortOfTestingCamera.InputSelection"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="InputSelection" WindowStartupLocation="CenterOwner" ResizeMode="NoResize" ShowInTaskbar="False" mc:Ignorable="d" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" SizeToContent="WidthAndHeight" d:DesignWidth="280" d:DesignHeight="206">

        <StackPanel HorizontalAlignment="Center" Name="stackPanel1" VerticalAlignment="Top" Margin="10" MaxWidth="500">
            <GroupBox Header="Select Camera" HorizontalAlignment="Center" VerticalAlignment="Center">
                <ComboBox Height="23" Name="comboBox1" HorizontalAlignment="Center" VerticalAlignment="Center" MinWidth="120" />
            </GroupBox>
            <Button Content="OK" Name="ButtonOK" IsDefault="True" Click="ButtonOK_Click" />
        </StackPanel>
</Window>

Answer 1

It seems to be a rendering artifact that occurs when the window is resized to the width of your combo box when the content string is set.

If you add the attribute SnapsToDevicePixels="True" to the Window-tag the black line goes away.