ItemContainerStyle中的绑定有效，DataTemplate中的绑定没有 - 如何修复？

我有一个自定义选项卡控件，它在TabItem中显示一个框架，以及一个自定义标头 . 在ItemContainerStyle中设置绑定以显示TabItem有效，但我无法在DataTemplate中获取绑定以将 Headers 文本设置为正常工作 . 请注意，TabControl绑定到项目的ObservableCollection，其中包含两个属性 - TI（要在TabItem中显示的帧）和DisplayName（要在 Headers 中显示的字符串） .

=============== XAML ================

<TabControl Height="Auto" Name="mainTabControl" Width="Auto" IsSynchronizedWithCurrentItem="True" Margin="4" >
  <TabControl.ItemTemplate>
    <DataTemplate>
      <DockPanel Width="Auto">
        <Button 
            Content="X"
            Cursor="Hand"
            DockPanel.Dock="Right"
            Focusable="False"
            FontFamily="Courier" 
            FontSize="9"
            FontWeight="Bold"  
            Margin="0,1,0,0"
            Padding="0"
            VerticalContentAlignment="Bottom"
            Width="16" Height="16"               
            >
          <!-- Command=""      //Command binding TBD later
            CommandParameter="" -->
        </Button>
        <ContentPresenter 
            Content ="{Binding DisplayName}"
            VerticalAlignment="Center" 
            Margin="0,0,7,0"
          />
      </DockPanel>
    </DataTemplate>
  </TabControl.ItemTemplate>

  <TabControl.Style>
    <Style TargetType="TabControl">
      <Style.Triggers>
        <DataTrigger Binding="{Binding Items.Count, RelativeSource={RelativeSource Self}}"
                        Value="0">
          <Setter Property="Visibility" Value="Hidden" />
        </DataTrigger>
      </Style.Triggers>
    </Style>
  </TabControl.Style>
  <TabControl.ItemContainerStyle  >
    <Style TargetType="TabItem">
      <Setter Property="Content" Value="{Binding TI}"/>
    </Style>
  </TabControl.ItemContainerStyle>
</TabControl>

============ BOUND ITEM =============

class TabItemContainer : Frame
  {
    public event DependencyPropertyChangedEventHandler PropertyChanged;

    private void NotifyPropertyChanged(String info)
    {
      if (PropertyChanged != null)
      {
        PropertyChanged(this, new DependencyPropertyChangedEventArgs());
      }
    }

    private string displayname;

    public string DisplayName
    {
      get { return displayname; }
      set
      {
        if (value != this.displayname)
        {
          displayname = value;
          NotifyPropertyChanged("DisplayName");
        }
      }
    }

    public Frame TI { get; set; }
  }

===========代码背后=============

ObservableCollection<TabItemContainer> Tablist;

public MainWindow()
{
  InitializeComponent();

  Tablist = new ObservableCollection<TabItemContainer>();

  TabItemContainer tic = new TabItemContainer();
  tic.DataContext = tic;
  tic.DisplayName = "Untitled";
  tic.TI = new Frame();
  tic.TI.Navigate(new Page1());
  Tablist.Add(tic);
  mainTabControl.ItemsSource = Tablist;
  mainTabControl.SelectedIndex = Tablist.Count - 1;
}