Wpf DataGrid ToolTip for column headers

Question

I have a tooltip for datagrid cells which is open when cell content is trimmed:

    private void grid2_MouseMove(object sender, MouseEventArgs e)
    {
        DependencyObject dep = (DependencyObject)e.OriginalSource;

        while ((dep != null) &&
                !(dep is DataGridCell) && !(dep is DataGrid))
        {
            if (dep is Run)
                continue;

            dep = VisualTreeHelper.GetParent(dep);
        }

        if (dep == null)
            return;

        if (dep is DataGridCell)
        {
            DataGridCell cell = dep as DataGridCell;
            var x = cell.Content as TextBlock;

            if (x.Text != check)
                tlp.IsOpen = false;

            if (x != null)
            {
                FormattedText formattedText = new FormattedText(x.Text,
                System.Threading.Thread.CurrentThread.CurrentCulture,
                FlowDirection.LeftToRight,
                new Typeface(x.FontFamily.ToString()),
                x.FontSize,
                Brushes.Black);

                if (formattedText.Width > Convert.ToDouble(cell.Column.ActualWidth.ToString()) - 3)
                {
                    tlp.Content = x.Text;
                    tlp.IsOpen = true;
                    check = x.Text;
                }
            }
        }

        if (dep is DataGrid)
            if (tlp.IsOpen == true)
                tlp.IsOpen = false;
    }

I want to do the same for column headers, but i don't know how. There is no such object like "DataGridColumnHeader" for example... Help me, please?

Answer 1

So, i finded a solution. I just replaced ContentPresenter with my textblock with custom tooltip in default DataGridHeader style:

<TextBlock Text="{Binding}" TextTrimming="CharacterEllipsis">
    <TextBlock.ToolTip>
        <ToolTip Visibility="{Binding RelativeSource={RelativeSource Self}, Path=PlacementTarget, Converter={StaticResource trimmedVisibilityConverter}}">
            <ToolTip.Content>
                <TextBlock Text="{Binding}"/>
            </ToolTip.Content>
        </ToolTip>
    </TextBlock.ToolTip>
</TextBlock>

And converter:

public class TrimmedTextBlockVisibilityConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value == null) return Visibility.Collapsed;

        FrameworkElement textBlock = (FrameworkElement)value;

        textBlock.Measure(new System.Windows.Size(Double.PositiveInfinity, Double.PositiveInfinity));

        if (((FrameworkElement)value).ActualWidth < ((FrameworkElement)value).DesiredSize.Width)
            return Visibility.Visible;
        else
            return Visibility.Collapsed;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

I don't know it is good solution or not, but it works exactly like i need... Thanks everyone for the answers.