It does the trick!  Thank you very very much!!

Hi,

As I see the image, the FillSceneGraph is what you need. Here is a sample code with a sample data which adds a textbox to the before last point of the polyline. Please, review it and let me know if you need a further assistance.

protected void Page_Load(object sender, EventArgs e)
{
    UltraChart UltraChart1 = new UltraChart();           
    this.Form.Controls.Add(UltraChart1);
 
    UltraChart1.ChartType = ChartType.ScatterLineChart;           

    DataTable lineData = new DataTable();
    lineData.Columns.Add("label", typeof(string));
    lineData.Columns.Add("Value", typeof(double));

    DataTable scatterData = new DataTable();
    scatterData.Columns.Add("ValueX", typeof(double));
    scatterData.Columns.Add("ValueY", typeof(double));

    lineData.Rows.Add(new object[] { "item 1", 10 });
    lineData.Rows.Add(new object[] { "item 2", 11 });
    lineData.Rows.Add(new object[] { "item 3", 12 });
    lineData.Rows.Add(new object[] { "item 4", 11 });
    lineData.Rows.Add(new object[] { "item 5", 13 });

    scatterData.Rows.Add(new object[] { 2, 2 });
    scatterData.Rows.Add(new object[] { 4, 4 });
    scatterData.Rows.Add(new object[] { 6, 6 });
    scatterData.Rows.Add(new object[] { 8, 8 });

    UltraChart1.ScatterLineChart.LineData.DataSource = lineData;//dt1;
    UltraChart1.ScatterLineChart.LineData.SwapRowsAndColumns = true;
    UltraChart1.ScatterLineChart.LineData.DataBind();
   
    DataTable dt = new DataTable();
    dt.Columns.Add("X-Axis", typeof(decimal));
    dt.Columns.Add("Y-Axis", typeof(decimal));
    dt.Rows.Add(new object[] { 6.5, 80 });
    dt.Rows.Add(new object[] { 20, 90 });

    UltraChart1.ScatterLineChart.ScatterData.DataSource = scatterData;// dt;
    UltraChart1.ScatterLineChart.ScatterData.DataBind();
    UltraChart1.ScatterLineChart.Scatter.ColumnX = 0;
    UltraChart1.ScatterLineChart.Scatter.ColumnY = 1;

    UltraChart1.ScatterLineChart.LineData.UseRowLabelsColumn = true;
    UltraChart1.ScatterLineChart.LineData.RowLabelsColumn = 0;

    UltraChart1.Data.DataBind();
    UltraChart1.FillSceneGraph += new Infragistics.UltraChart.Shared.Events.FillSceneGraphEventHandler(UltraChart1_FillSceneGraph);
}

void UltraChart1_FillSceneGraph(object sender, Infragistics.UltraChart.Shared.Events.FillSceneGraphEventArgs e)
{
    List<Text> texts = new List<Text>();
    // loop trough the scene graph collection to get all polylines and create text box with
    // start coordinates the before last point coordinates
    foreach (Primitive p in e.SceneGraph)
    {
        Polyline line = p as Polyline;
        if (line == null)
        {
            continue;
        }

        LineLayer lineLayer = line.Layer as LineLayer;
        if (lineLayer != null)
        {                   
             // get the desired text you want to add to the line -> you could get whatever data you want to display
            String textString = lineLayer.ChartData.GetColumnLabel(line.Column).ToString();
            // find the coordinates of the point we want to add the text too
            Point beforeLastPoint = line.points[line.points.Length - 2].point;
            Text text = new Text();
            text.PE.Fill = Color.Red;
            // set the bounds of the text to be a rectangle with start point the before last point
            // you can set whatever coordinates you need
            text.bounds = new Rectangle(beforeLastPoint.X, beforeLastPoint.Y, 100, 20);
            text.SetTextString(textString);
            texts.Add(text);
        }
    }

    foreach (Text t in texts)
    {
        e.SceneGraph.Add(t);
    }
}

By the way, you might have to click the graph to zoom in to find the line labels truncated by screen.