How to find ItemTemplate from DataTemplate of TabItem - wpf

Question

I am trying to set a trigger in my DataTemplate so that when the source object has a property HasUnreadMessages set to true, then the header text goes red. But from inside the triggers in datatemplate I have no idea of how to reference the TextBlock of the header.
Full Code :
<Window x:Class="IRC.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:loc="clr-namespace:IRC"
Title="" Height="350" Width="525">
<Window.Resources>
<DataTemplate DataType="{x:Type loc:Tab}">
<DockPanel>
<ListBox x:Name="lstUsers" ItemsSource="{Binding Users}" Visibility="Collapsed" DockPanel.Dock="Right" />
<ListBox x:Name="lstMessage" ItemsSource="{Binding Messages}" />
</DockPanel>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding Type}" Value="Channel">
<Setter TargetName="lstUsers" Property="Visibility" Value="Visible" />
</DataTrigger>
<DataTrigger Binding="{Binding HasUnreadMessages}" Value="True">
<Setter TargetName="tabHeader" Property="Foreground" Value="Red" /> // -- ERROR
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</Window.Resources>
<DockPanel>
<Menu DockPanel.Dock="Top">
<MenuItem Header="_Actions">
<MenuItem Header="_Connect" InputGestureText="Alt+C" Click="Connect" />
</MenuItem>
</Menu>
<TextBox Name="txtInput" Height="22" VerticalContentAlignment="Center" SpellCheck.IsEnabled="True" DockPanel.Dock="Bottom" />
<TabControl Name="pnlTabs" ItemsSource="{Binding}" ContentTemplate="{Binding}" DockPanel.Dock="Top">
<TabControl.ItemTemplate>
<DataTemplate>
<TextBlock x:Name="tabHeader" Text="{Binding Name}"/>
</DataTemplate>
</TabControl.ItemTemplate>
</TabControl>
</DockPanel>
</Window>
Error :
The name "tabHeader" is not recognized.
The member "Foreground" is not recognized or is not accessible.
Tab :
public class Tab
{
public string Name { get; set; }
public string Type { get; set; }
public ObservableCollection<string> Users { get; set; }
public ObservableCollection<string> Messages { get; set; }
public bool HasUnreadMessages { get; set; }
}

Answer 1

You're trying to change a property of an object which is not known at that point.
Instead of putting the DataTrigger on the Tab, move the DataTrigger to the TabItem - since it's the TabItem that you're trying to change...
In your case, add a TabItem style:
<Window.Resources>
<DataTemplate DataType="{x:Type TabItem}" x:Key="ItemTemplateStyle">
<TextBlock x:Name="tabHeader" Text="{Binding Name}"/>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding HasUnreadMessages}" Value="True">
<Setter TargetName="tabHeader" Property="Foreground" Value="Red" />
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
And set this style for the TabItems:
<TabControl Name="pnlTabs" ItemsSource="{Binding}" ContentTemplate="{Binding}" DockPanel.Dock="Top"
ItemTemplate="{StaticResource ItemTemplateStyle}" />