Please help me ,thanks a lot

 How to draw a trend line ? like excel trend line

like this-->>

this is my file.cs ,use the Composite Chart ,but i don't know how to draw a trend line

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using System.Data.OracleClient;
using System.Web.Configuration;
using Infragistics.UltraChart.Shared.Styles;
using Infragistics.UltraChart.Resources.Appearance;
using Infragistics.UltraChart.Core.Layers;
using Infragistics.UltraChart.Resources;

/// <summary>
///
/// </summary>
public partial class DescCurve : System.Web.UI.Page,IRenderLabel
{
    DataSet ds = new DataSet();
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {

            try
            {
                /*return dataset
                 *
                 *
                    NY                         XHD2       XHA2       XHE2
                    -------------------- ---------- ---------- ----------
                    200001                     6885       1163       6035
                 *
                 *
                */
                OracleConnection conn = new OracleConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString);
                string s = "select Ny,sum(case when t.dydm='XHD2' then t.ycyl else 0 end) as XHD2,sum(case when t.dydm='XHA2' then t.ycyl else 0 end) as XHA2,sum(case when t.dydm='XHE2' then t.ycyl else 0 end) as XHE2 FROM pgxx_data_monthly t where ny like '200%' and (t.dydm='XHD2' or t.dydm='XHA2' or t.dydm='XHE2') group by ny order by ny asc";
                OracleDataAdapter sa = new OracleDataAdapter(s, conn);
                conn.Open();
                sa.Fill(ds, "QuerySelect");
                conn.Close();

                // Chart     
                UltraChart1.DataSource = ds;
                UltraChart1.DataBind();
                //Response.Write(ds.Tables[0].Columns[0].ToString());
                //Response.End();
                UltraChart1.ChartType = ChartType.Composite;
                UltraChart1.Width = 1024;
                UltraChart1.Height = 600;
                UltraChart1.TitleTop.Text = "desccurve";
                UltraChart1.EnableCrossHair = true;
                UltraChart1.EmptyChartText = "data false!";

                // add chartarea
                ChartArea myChartArea = new ChartArea();
                UltraChart1.CompositeChart.ChartAreas.Add(myChartArea);

                //add axis
                AxisItem myX = new AxisItem();
                myX.OrientationType = AxisNumber.X_Axis;
                myX.DataType= AxisDataType.String;
                myX.Labels.ItemFormatString = "<ITEM_LABEL>";
                //
                //http://help.infragistics.com/Help/NetAdvantage/NET/2007.3/CLR2.0/html/Chart_Creating_a_Composite_Chart_in_Code_Part_1_of_2.html
                myX.SetLabelAxisType = SetLabelAxisType.ContinuousData;

                AxisItem myY = new AxisItem();
                myY.OrientationType = AxisNumber.Y_Axis;
                myY.DataType = AxisDataType.Numeric;
                myY.Labels.ItemFormatString = "<DATA_VALUE:00.##>";

                myChartArea.Axes.Add(myX);
                myChartArea.Axes.Add(myY);

                //add series to Series collection.
                NumericSeries myseries1 = new NumericSeries();
                myseries1.Label = "SeriesA";
                //data bound
                myseries1.Data.DataSource = ds.Tables[0];
                myseries1.Data.LabelColumn = ds.Tables[0].Columns[0].ToString();
                myseries1.Data.ValueColumn = ds.Tables[0].Columns[1].ToString();
                //myseries1.Data.LabelColumn = "NY";
                //myseries1.Data.ValueColumn = "XHD2";
                UltraChart1.CompositeChart.Series.Add(myseries1);

                NumericSeries myseries2 = new NumericSeries();
                myseries2.Label = "SeriesB";
                myseries2.Data.DataSource = ds.Tables[0];
                myseries2.Data.LabelColumn = ds.Tables[0].Columns[0].ToString();
                myseries2.Data.ValueColumn = ds.Tables[0].Columns[2].ToString();
                UltraChart1.CompositeChart.Series.Add(myseries2);

                NumericSeries myseries3 = new NumericSeries();
                myseries3.Label = "SeriesC";
                myseries3.Data.DataSource = ds.Tables[0];
                myseries3.Data.LabelColumn = ds.Tables[0].Columns[0].ToString();
                myseries3.Data.ValueColumn = ds.Tables[0].Columns[3].ToString();
                UltraChart1.CompositeChart.Series.Add(myseries3);

                //add chart layer
                ChartLayerAppearance mylayer = new ChartLayerAppearance();
                mylayer.ChartType = ChartType.LineChart;
                mylayer.ChartArea = myChartArea;
                mylayer.AxisX = myX;
                mylayer.AxisY = myY;
                mylayer.Series.Add(myseries1);
                mylayer.Series.Add(myseries2);
                mylayer.Series.Add(myseries3);
                this.UltraChart1.CompositeChart.ChartLayers.Add(mylayer);

                //custom Tooltips 

                UltraChart1.Tooltips.Display = TooltipDisplay.MouseMove; 
                UltraChart1.Tooltips.Format = TooltipStyle.Custom;
                UltraChart1.Tooltips.FormatString = "<CUSTOM>";
                Hashtable labelHash = new Hashtable();
                labelHash.Add("CUSTOM", this);
                this.UltraChart1.LabelHash = labelHash;
            }
            finally
            {

            }
        }
    }

    #region IRenderLabel

    string IRenderLabel.ToString(Hashtable Context)
    {
        double displayY=(double)Context["DATA_VALUE"];
        string dispayX=(string)Context["ITEM_LABEL"];
        string customLabel = "";
        //return label 
        customLabel = displayY + "，" +dispayX ;
        //customLabel = "OK";
        return customLabel;
    }

    #endregion