How to get parent nodes in data grid group expander header

I have a datagrid with grouped data in a WPF application. For the group header, I have a context menu to delete the group. The item source of the datagrid is bind with my object. How to detect the parent/ parents group of the expander header? I have tried to do like this but it returns null.

private void buttonDeleteHeader_Click(object sender, RoutedEventArgs e)
{
    MenuItem menuItem = sender as MenuItem;
    TextBlock header = menuItem.Parent as TextBlock;
}

Grouping of Data

m_infoList = new ObservableCollection<MyDataObject>();
m_infoList .Add(new MyDataObject
        { ID = 1, Attr1 = "Level1",  Attr2 = "Level2", Attr3 ="Level3", Attr4 = "Child1"});
 m_infoList .Add(new MyDataObject
        { ID = 2, Attr1 = "Level1",  Attr2 = "Level2", Attr3 ="Level3", Attr4 = "Child2"});
CollectionView collectionView = (CollectionView)CollectionViewSource.GetDefaultView(m_infoList);
            PropertyGroupDescription groupDescription1 = new PropertyGroupDescription("Attr1");
            PropertyGroupDescription groupDescription2 = new PropertyGroupDescription("Attr2");
            PropertyGroupDescription groupDescription3 = new PropertyGroupDescription("Attr3");
            collectionView.GroupDescriptions.Clear();
            collectionView.GroupDescriptions.Add(groupDescription1);
            collectionView.GroupDescriptions.Add(groupDescription2);
            collectionView.GroupDescriptions.Add(groupDescription3);

Data Grid codes

    <DataGrid x:Name="dataGrid"
                  ItemsSource="{Binding InfoList, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" ....>
    ...
    <DataGrid.GroupStyle>
                <GroupStyle>
                    <GroupStyle.ContainerStyle>
                        <Style TargetType="{x:Type GroupItem}">
                            <Setter Property="Template">
                                <Setter.Value>
                                    <ControlTemplate>
                                        <Expander x:Name="MyExpander" IsExpanded="True">
                                            <Expander.Header>
                                                <StackPanel Orientation="Horizontal">                       
                                                    <TextBlock x:Name="MyExpanderHeader" Text="{Binding Name}" FontWeight="Bold" VerticalAlignment="Bottom"
                                                               ToolTip="Right click to delete">
                                                        <TextBlock.ContextMenu>
                                                            <ContextMenu>
                                                                <MenuItem Header="Delete" Click="buttonDeleteHeader_Click">

                                                                </MenuItem>
                                                            </ContextMenu>
                                                        </TextBlock.ContextMenu>
                                                    </TextBlock>
                                                </StackPanel>
                                            </Expander.Header>
                                            <ItemsPresenter Margin="20,0,0,0"/>
                                        </Expander>
                                    </ControlTemplate>
                                </Setter.Value>
                            </Setter>
                        </Style>
                    </GroupStyle.ContainerStyle>
                </GroupStyle>
            </DataGrid.GroupStyle>
    </DataGrid>

Solution

Do this :

MenuItem item = sender as MenuItem;
ContextMenu ctxMenu = (ContextMenu) item.Parent;

// ctxMenu.Parent will give you `Popup` 

TextBlock tb = (TextBlock) ctxMenu.PlacementTarget;

To traverse the levels, you can use RelativeSource and its AncestorLevel property if you are using Binding, and programmatically you can use VisualTreeHelper class and traverse up like this :

 DependencyObject parent = VisualTreeHelper.GetParent(tb);
 while (parent.GetType() != typeof(Expander))
        parent = VisualTreeHelper.GetParent(parent);

Use Snoop tool to inspect the visual tree, and traverse accordingly.