Style Datagrid Header border issue - wpf

Question

I try to style datagridcolumn header but at the top right I have a double border.
I try to play with margin but it doesn't work I have always this double border at runtime.
How I can avoid this?
<Style TargetType="{x:Type DataGridRow}">
<Setter Property="Background" Value="{StaticResource BrushAbbGrey255}" />
<Setter Property="FontFamily" Value="ABBVoice" />
</Style>
<Style TargetType="{x:Type DataGridCell}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DataGridCell}">
<Border Padding="7,5,7,4">
<ContentPresenter VerticalAlignment="Center"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style TargetType="{x:Type DataGridColumnHeader}">
<Setter Property="Foreground" Value="{StaticResource BrushAbbGrey90}" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DataGridColumnHeader}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<Border x:Name="BackgroundBorder"
BorderThickness="1,1,1,1"
Margin="-1,0,0,0"
Background="{StaticResource BrushAbbGrey240}"
BorderBrush="{StaticResource BrushAbbGrey200}"
Grid.ColumnSpan="2" />
<ContentPresenter Margin="8,10,7,10" VerticalAlignment="Center"/>
<Path x:Name="SortArrow" Visibility="Collapsed" Data="M0,0 L1,0 0.5,1 z" Stretch="Fill"
Grid.Column="1" Width="8" Height="6" Fill="White" Margin="0,0,8,0"
VerticalAlignment="Center" RenderTransformOrigin="0.5,0.4" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

Answer 1

Try to set the right-margin to -1:
<Style TargetType="{x:Type DataGridColumnHeader}">
<Setter Property="Foreground" Value="{StaticResource BrushAbbGrey90}" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DataGridColumnHeader}">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<Border x:Name="BackgroundBorder"
BorderThickness="1,1,1,1"
Margin="-1,0,-1,0"
Background="{StaticResource BrushAbbGrey240}"
BorderBrush="{StaticResource BrushAbbGrey200}"
Grid.ColumnSpan="2" SnapsToDevicePixels="True" />
<ContentPresenter Margin="8,10,7,10" VerticalAlignment="Center"/>
<Path x:Name="SortArrow" Visibility="Collapsed" Data="M0,0 L1,0 0.5,1 z" Stretch="Fill"
Grid.Column="1" Width="8" Height="6" Fill="White" Margin="0,0,8,0"
VerticalAlignment="Center" RenderTransformOrigin="0.5,0.4" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
You may also want to set the SnapsToDevicePixels property of the Border to true.

Answer 2

I added a style for my datagrid to set RowHeaderWidth to 1 and it's working fine.
<Style TargetType="{x:Type DataGrid}">
<Setter Property="BorderBrush" Value="{StaticResource BrushAbbGrey200}" />
<Setter Property="HorizontalGridLinesBrush" Value="{StaticResource BrushAbbGrey200}" />
<Setter Property="VerticalGridLinesBrush" Value="{StaticResource BrushAbbGrey200}" />
<Setter Property="BorderThickness" Value="1,0" />
<Setter Property="RowHeaderWidth" Value="1" />
</Style>