Tab Item and Tab Control Border Style - wpf

Question

How do I style the Tab Control Border so that the selected Tab Item does not have a line underneath it?
These are my Tab Control and Tab Item styles so far.
<!-- Tab control styling -->
<Style TargetType="{x:Type TabControl}">
<Setter Property="Padding" Value="10,5,10,5" />
<Setter Property="Margin" Value="3.5" />
<Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.ControlLightBrushKey}}" />
</Style>
<!-- Tab item styling -->
<Style TargetType="{x:Type TabItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabItem}">
<Grid>
<Border
Name="Border"
Background="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"
BorderBrush="Black"
BorderThickness="1,1,1,0"
CornerRadius="3,3,0,0"
MinWidth="120">
<ContentPresenter x:Name="ContentSite"
VerticalAlignment="Center"
HorizontalAlignment="Center"
ContentSource="Header"
Margin="12,2,12,2"/>
</Border>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsFocused" Value="True" >
<Setter Property="Background" TargetName="Border" Value="{DynamicResource {x:Static SystemColors.ControlLightBrushKey}}" />
<Setter Property="HeaderTemplate">
<Setter.Value>
<DataTemplate>
<TextBlock FontWeight="Bold" Text="{Binding}"/>
</DataTemplate>
</Setter.Value>
</Setter>
</Trigger>
<Trigger Property="IsMouseOver" Value="True" >
<Setter Property="Background" TargetName="Border" Value="{DynamicResource {x:Static SystemColors.ControlLightBrushKey}}" />
<Setter Property="HeaderTemplate">
<Setter.Value>
<DataTemplate>
<TextBlock FontWeight="Bold" Text="{Binding}"/>
</DataTemplate>
</Setter.Value>
</Setter>
</Trigger>
<Trigger Property="IsSelected" Value="True" >
<Setter Property="Background" TargetName="Border" Value="{DynamicResource {x:Static SystemColors.ControlLightBrushKey}}" />
<Setter Property="HeaderTemplate">
<Setter.Value>
<DataTemplate>
<TextBlock FontWeight="Bold" Text="{Binding}"/>
</DataTemplate>
</Setter.Value>
</Setter>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
If I can achieve the look displayed in the screenshot without having to overload the tab item control template then I don't have an issue as the default tab item template doesn't have the line underneath it on the selected tab. I haven't been able to do this so far. Thanks for your help.

Answer 1

The XAML below is how I have overridden the TabControl to solve this problem. The key piece of info is the Margin property of the HeaderPanel. You will see that the bottom margin is -1, which shifts it down just enough to cover up that line.
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabControl}">
<Grid KeyboardNavigation.TabNavigation="Local">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<TabPanel x:Name="HeaderPanel"
Grid.Row="0"
Panel.ZIndex="1"
Margin="0,0,4,-1"
IsItemsHost="True"
KeyboardNavigation.TabIndex="1"
Background="Transparent" />
<Border x:Name="Border"
Grid.Row="1"
BorderThickness="1"
KeyboardNavigation.TabNavigation="Local"
KeyboardNavigation.DirectionalNavigation="Contained"
KeyboardNavigation.TabIndex="2">
<Border.Background>
<SolidColorBrush Color="White"/>
</Border.Background>
<Border.BorderBrush>
<SolidColorBrush Color="White"/>
</Border.BorderBrush>
<ContentPresenter x:Name="PART_SelectedContentHost"
Margin="4"
ContentSource="SelectedContent" />
</Border>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

Answer 2

Add property Padding="0,0,0,0" to tab control :-)

Answer 3

Instead of modifying tabcontrol template, you may as well just modify the TabItem template, by adding two lines to cover up the border, and using minus margins for covering up.
(Please take a look at "TopLineCover" and "BottomLineCover" borders.)
<Style TargetType="TabItem" BasedOn="{StaticResource {x:Type TabItem}}">
<Setter Property="Foreground" Value="{DynamicResource VsBrush.WindowText}"/>
<Setter Property="Background" Value="{DynamicResource VsBrush.Window}"/>
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
<Setter Property="VerticalContentAlignment" Value="Stretch"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabItem}">
<Grid SnapsToDevicePixels="true">
<Border x:Name="HeaderBorder" Padding="8,3,8,3" BorderThickness="1,1,1,0"
Background="{DynamicResource {x:Static commonControls:ColorService.JobViewHeaderBrushKey}}"
BorderBrush="{DynamicResource {x:Static commonControls:ColorService.JobViewHeaderBorderBrushKey}}">
<ContentPresenter x:Name="Content" ContentSource="Header"
HorizontalAlignment="{Binding Path=HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"
VerticalAlignment="{Binding Path=VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"
/>
</Border>
<Border x:Name="TopLineCover" BorderThickness="1,1,1,0" Margin="0,-2,0,0" Height="3" Panel.ZIndex="100"
Background="{DynamicResource VsBrush.Window}" BorderBrush="{DynamicResource {x:Static commonControls:ColorService.JobViewHeaderBorderBrushKey}}"
VerticalAlignment="Top" HorizontalAlignment="Stretch" Visibility="Collapsed"/>
<Border x:Name="BottomLineCover" BorderThickness="0,0,0,3" Margin="1,0,1,-2" Panel.ZIndex="100" BorderBrush="{DynamicResource VsBrush.Window}"
VerticalAlignment="Bottom" HorizontalAlignment="Stretch" Visibility="Collapsed"/>
</Grid>
<ControlTemplate.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsMouseOver" Value="True"/>
<Condition Property="IsSelected" Value="False"/>
</MultiTrigger.Conditions>
<Setter Property="Background" TargetName="HeaderBorder" Value="{DynamicResource VsBrush.Window}"/>
</MultiTrigger>
<Trigger Property="IsSelected" Value="True">
<Setter Property="Background" TargetName="HeaderBorder" Value="{DynamicResource VsBrush.Window}"/>
<Setter Property="Visibility" TargetName="TopLineCover" Value="Visible"/>
<Setter Property="Visibility" TargetName="BottomLineCover" Value="Visible"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

Answer 4

In the past I've accomplished this by making the TabItem extend a little further down then it's allocated, so its actually drawn on top of the border element and hides it
I can't remember how I did it exactly, but I think it was with a negative margin on the bottom of the TabItem