Display data in mousehover

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C#

ASP.NET

Telerik

hi,
im using control rahhtml chart telerik in my project this is my code

SqlConnection con = new SqlConnection(@"Data Source=.;Initial Catalog=DB_WEB_Q_TEL;Integrated Security=True");
string req = "select time_tag,[ain_sebou|Niveau] as AIN_SEBOU_NIVEAU from QTSW_DATA1 where time_tag between ('01/01/2015') AND ('10/01/2015')";
DataSet DS = new DataSet();
con.Open();
if (DS.Tables.Contains("TRChart"))
{
DS.Tables.Remove("TRChart");
}
SqlDataAdapter da = new SqlDataAdapter(req, con);
da.Fill(DS, "TRChart");
con.Close();

RadHtmlChart chart = new RadHtmlChart();

chart.DataSource = DS.Tables["TRChart"];
chart.DataBind();

LineSeries LS = new LineSeries();
LS.DataFieldY = "AIN_SEBOU_NIVEAU";
LS.TooltipsAppearance.DataFormatString = "{0} at {1}";

chart.PlotArea.XAxis.LabelsAppearance.DataFormatString = "{0:dd-MM-yyyy HH:mm}";
chart.PlotArea.XAxis.LabelsAppearance.RotationAngle = 90;

chart.PlotArea.XAxis.BaseUnit = Telerik.Web.UI.HtmlChart.DateTimeBaseUnit.Days;
chart.PlotArea.XAxis.DataLabelsField = "time_tag";
chart.PlotArea.Series.Add(LS);

PlaceHolder3.Controls.Add(chart);

<asp:PlaceHolder ID="PlaceHolder3" runat="server">


        </asp:PlaceHolder>

it works but when i want to see the value in date time at my line don't apear for understanding mee plz see this pic

http://www.mediafire.com/view/hu8jnj5kckhbc1q/ChartHover.png[^]

i want to display for example ( 230 at 01/01/2015 00:00 )
plz i need help