WPF Dock Panel wierd magin

Question

I have a very simple dockpanel inside a border. But the dock panel seems to have a 1px margin on the right and bottom. I cant seem to get rid of it by setting the margin or the dockpanel nor by setting the padding of the border.

What exactly is causing it and how can I fix it without hacking it (IE negative margin on the dock panel)

<Window x:Class="WPFTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d"
        Height="350" Width="525">
    <Grid>
        <Border BorderBrush="Black" BorderThickness="2" Padding="0">
            <DockPanel Background="Blue" Margin="0"/>
        </Border>
    </Grid>
</Window>

No style defined on Border or DockPanel. Tried this on a brand new project and still seeing the white lines

Answer 1

The usual way you get gaps like that in XAML is becasue the UI is being scaled. If you can't find anything that might be scaling it ( RenderTransform in a parent, OS settings such as font size, probably other stuff), you could try playing with UseLayoutRounding and SnapsToDevicePixels .