How to fetch control from DataTemplate when DataTemplate in XAML is customized

Question

Can anyone explain how to get the control specified in the DataTemplate when the tabs are added at run-time and the TabControl has been customized in XAML to use plain class as data source? Here is the scenario.

I have a class

public class TabContent
{
    public string Header { get; set; }
    public string Code { get; set; }
    public bool Modified { get; set; }
}

Here is the XAML customization of TabControl:

<TabControl x:Name="tabControl" SelectionChanged="tabControl_SelectionChanged">
    <!-- Header -->
    <TabControl.ItemTemplate>
        <DataTemplate>
            <TextBlock x:Name="txtHeader" Text="{Binding Header}" />
        </DataTemplate>
    </TabControl.ItemTemplate>

    <!-- Content -->
    <TabControl.ContentTemplate>
        <DataTemplate>
            <!-- Code -->
            <ScrollViewer HorizontalScrollBarVisibility="Visible" VerticalScrollBarVisibility="Visible">
                <DockPanel>
                    <ListBox x:Name="lbLines" Width="Auto"
                             Margin="2,3.1,2,2"
                             FontFamily="Consolas"
                             HorizontalContentAlignment="Right">
                    <!-- ...snip.. -->
                    </ListBox>

                    <TextBox x:Name="editor"
                             Text="{Binding Code}"
                             AcceptsReturn="True" AcceptsTab="True"
                             ScrollViewer.VerticalScrollBarVisibility="Disabled"
                             ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                             FontFamily="Consolas">
                    </TextBox>
                </DockPanel>
            </ScrollViewer>
        </DataTemplate>
    </TabControl.ContentTemplate>

</TabControl>

And, here is the text in code behind:

ObservableCollection<TabContent> _tabContents = new ObservableCollection<TabContent>();

//In constructor..
public MainWindow() {
    tabControl.ItemsSource = _tabContents;
}

void loadTab() {
    var t = new TabContent()
    {
        Header = "Code File 1",
        Code = File.ReadAllText(@"C:\code.txt")
    };
    _tabContents.Add(t);
    tabControl.SelectedItem = tabControl.Items[tabControl.Items.Count - 1];
}

Now, when user clicks on a tab, I want to get the textbox control in it.

private void tabControl_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    //how do I get the "editor" textbox  and "lbLines" ListBox objects ???
}

=================

Why MSDN method doesn't work here: http://msdn.microsoft.com/en-us/library/bb613579(v=vs.110).aspx

The items in the TabControl are of type TabContent and not TabItem. So, the MSDN example fails to fetch the control as it doesn't meet the criteria: "in order to fetch the control, the template must be applied to the item." Here, TabContent is plain class, and cannot have template applied on it.