how to print multi charts on one page?

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MVC

chart

this gives me headache...-_-..

I have a view ..

foreach(var product in Model)
{
 ....
  <% Html.RenderAction("GetChartData", "Inventory", new { productId = product.ProductID}); %>
   <% Html.RenderPartial("ChartView");%>
 ....

 }

in "GetChartData" method which is in controller..
I set data in sessions..
for example..

if (order1.ToList().Count() == 0)
  {
      Session["order1"] = 0;
  }
  else
  {
      Session["order1"] = order1.ToList()[0].Qty;
  }

if (order2.ToList().Count() == 0)
  {
      Session["order2"] = 0;
  }
  else
  {
      Session["order2"] = order2.ToList()[0].Qty;
  }
  .......

and on "ChartView" usercontrol..

System.Web.UI.DataVisualization.Charting.Chart Chart2 = new System.Web.UI.DataVisualization.Charting.Chart();
    Chart2.Width = 500;
    Chart2.Height = 300;
    Chart2.RenderType = RenderType.ImageTag;
    Chart2.ImageStorageMode = ImageStorageMode.UseImageLocation;
    Chart2.ImageLocation = "~/temp";
    Chart2.Palette = ChartColorPalette.BrightPastel;
    Title t = new Title("Sold Qty In Weeks", Docking.Top, new System.Drawing.Font("Trebuchet MS", 7, System.Drawing.FontStyle.Bold), System.Drawing.Color.FromArgb(26, 59, 105));
    Chart2.Titles.Add(t);
    Chart2.ChartAreas.Add("Series 1");
    Chart2.Series.Add("Series 1");
    Chart2.Series["Series 1"].ChartType = SeriesChartType.FastLine;
    Chart2.Series["Series 1"].Points.AddY(Convert.ToInt32(Session["order1"]));
    Chart2.Series["Series 1"].Points.AddY(Convert.ToInt32(Session["order2"]));
    Chart2.Series["Series 1"].Points.AddY(Convert.ToInt32(Session["order3"]));
    ..........

    Chart2.Page = this.Page;
    HtmlTextWriter writer = new HtmlTextWriter(Page.Response.Output);
    Chart2.RenderControl(writer);
    Chart2.Dispose();

then when I load page.. I get all the same chart for each row. i think may be the last chart is overlapping all the previous charts.

when I debug, I am pretty sure that I get different values for each product.

I don't understand why this happens..

please help...