Silverlight whith SeparatorVisibility Collapsed in Headerstyle - silverlight

Question

I use the property "SeparatorVisibility" with the value "Collapsed" in a datagrid column header to disable the separator between the headers.
It works fine when my zoom is "normal" in my navigator :
but when zoom is using :
The separators are visible and I don't understand why!
Here my ressource dictionary:
<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:dataprimitives="clr-namespace:System.Windows.Controls.Primitives;assembly=System.Windows.Controls.Data"
xmlns:s="clr-namespace:System;assembly=mscorlib">
<!--Style de l'entête double ligne sans titre au dessus-->
<Style x:Name="HeaderDoubleLine" TargetType="dataprimitives:DataGridColumnHeader" >
<!--"#FFC9CACA"-->
<Setter Property="Foreground" Value="#FF000000"/>
<Setter Property="HorizontalContentAlignment" Value="Left"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="IsTabStop" Value="False"/>
<Setter Property="SeparatorBrush" Value="Transparent"/>
<Setter Property="SeparatorVisibility" Value="Collapsed"/>
<Setter Property="Padding" Value="8"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="dataprimitives:DataGridColumnHeader">
<Grid x:Name="Root">
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal"/>
<VisualState x:Name="MouseOver">
<Storyboard>
<ColorAnimation Duration="0"
Storyboard.TargetName="BackgroundRectangle"
Storyboard.TargetProperty="(Fill).Color" To="#FF448DCA"/>
<ColorAnimation Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Fill).(GradientStops)[3].Color" To="#7FFFFFFF"/>
<ColorAnimation Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Fill).(GradientStops)[2].Color" To="#CCFFFFFF"/>
<ColorAnimation Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Fill).(GradientStops)[1].Color" To="#F2FFFFFF"/>
</Storyboard>
</VisualState>
<VisualState x:Name="Pressed">
<Storyboard>
<ColorAnimation Duration="0"
Storyboard.TargetName="BackgroundRectangle"
Storyboard.TargetProperty="(Fill).Color" To="#FF448DCA"/>
<ColorAnimation Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Fill).(GradientStops)[0].Color" To="#D8FFFFFF"/>
<ColorAnimation Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Fill).(GradientStops)[1].Color" To="#C6FFFFFF"/>
<ColorAnimation Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Fill).(GradientStops)[2].Color" To="#8CFFFFFF"/>
<ColorAnimation Duration="0"
Storyboard.TargetName="BackgroundGradient"
Storyboard.TargetProperty="(Fill).(GradientStops)[3].Color" To="#3FFFFFFF"/>
</Storyboard>
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="SortStates">
<VisualState x:Name="Unsorted"/>
<VisualState x:Name="SortAscending" />
<VisualState x:Name="SortDescending" />
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Rectangle x:Name="BackgroundRectangle" Fill="#FF1F3B53" Stretch="Fill" Grid.ColumnSpan="2" />
<Rectangle x:Name="BackgroundGradient" Stretch="Fill" Grid.ColumnSpan="2">
<Rectangle.Fill>
<LinearGradientBrush EndPoint=".7,1" StartPoint=".7,0">
<GradientStop Color="#FCFFFFFF" Offset="0.015"/>
<GradientStop Color="#F7FFFFFF" Offset="0.375"/>
<GradientStop Color="#E5FFFFFF" Offset="0.6"/>
<GradientStop Color="#D1FFFFFF" Offset="1"/>
</LinearGradientBrush>
</Rectangle.Fill>
</Rectangle>
<StackPanel HorizontalAlignment="Stretch">
<Rectangle Margin="0,20,0,0" Fill="#FFC9CACA" VerticalAlignment="Stretch" Stretch="Fill" Width="Auto" Height="1" Visibility="Visible" />
<StackPanel Orientation="Horizontal" HorizontalAlignment="Stretch">
<Rectangle Margin="-1,0,0,0" Fill="#FFC9CACA" VerticalAlignment="Stretch" HorizontalAlignment="Right" Stretch="Fill" Width="1" Height="20" Visibility="Visible" />
<ContentPresenter Margin="5,0,0,0" Content="{TemplateBinding Content}" VerticalAlignment="Center" HorizontalAlignment="right"/>
</StackPanel>
</StackPanel>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I apply this style header on each column header that I want to change.

Answer 1

The only solution I found is to disable the browser zoom with the command : Application.Current.Host.Settings.EnableAutoZoom = false;. – Fabrice Mainguené Apr 2 at 9:43