TabItem ControlTemplate element Visibility - wpf

Question

I have defined a custom ControlTemplate for TabItem where I am having besides the ContentPresenter a Button (to hide the tab when clicked).
<Style TargetType="{x:Type TabItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TabItem">
<Border>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<ContentPresenter ContentSource="Header"/>
<Button Grid.Column="1" Content="x" Visibility="Visible"/>
</Grid>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I want the Button to be Visible only for certain TabItems and Collapsed for others. Collapsed state should be the default and I don't understand how to set it to Visible for certain tabs.
If the tab items are like
<TabItem Header="Normal tab">
<Grid />
</TabItem>
<TabItem Header="Closable tab">
<Grid/>
</TabItem>
and I want to have the "Closable tab" to be showing this Button but the "Normal tab" not showing this Button, how can this be done ?

Answer 1

You can use TabItem's Tag property to identify its type, and watch this type from inside Button with RelativeSource binding.
<TabControl>
<TabControl.Resources>
<Style TargetType="{x:Type TabItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TabItem">
<Border BorderThickness="1" BorderBrush="Green" Margin="1">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<ContentPresenter ContentSource="Header"/>
<Button Grid.Column="1" Content="x">
<Button.Style>
<Style TargetType="Button">
<Setter Property="Visibility" Value="Collapsed" />
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource AncestorType=TabItem}, Path=Tag}" Value="Closable">
<Setter Property="Visibility" Value="Visible" />
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
</Grid>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</TabControl.Resources>
<TabItem Header="Normal tab">
<Grid />
</TabItem>
<TabItem Tag="Closable" Header="Closable tab">
<Grid />
</TabItem>
</TabControl>
I edited Border attributes a little bit just to visual separate tabs, they are not necessary for this example to work.