I have a listbox with a bunch of contols in each list item.

<ListBox x:Name="projectList" IsSynchronizedWithCurrentItem="True">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                <TextBlock Text="{Binding Name}" />
                <ListBox x:Name="taskList" ItemsSource="{Binding Tasks}">
                    <ListBox.ItemTemplate>
                        <DataTemplate>
                            <StackPanel>
                                <TextBlock Text="{Binding Name}" />
                            </StackPanel>
                        </DataTemplate>
                    </ListBox.ItemTemplate>
                </ListBox>
                <TextBox x:Name="textBoxTask" />
                <Button
                    x:Name="ButtonAddNewTask"
                    Content="Test"
                    CommandParameter="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=DataContext}"
                    Click="ButtonAddNewTask_Click"
                    />
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

When I click on the button in the listbox i want to add a new item to the listbox within the listbox. I've come this far. So my question is how do I get hold of the textbox and how do I update the listbox?

Here is my click event

private void ButtonAddNewTask_Click(object sender, RoutedEventArgs e)
{
    Button button = (Button)sender;
    Project proj = button.DataContext as Project;
    if(proj.Tasks == null)
        proj.Tasks = new List<Task>();

    proj.Tasks.Add(new Task("Added Task"));
}

Thanx