Switching series in MSChart using AJAX

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C#

Visual-Studio

Ajax

chart

I have created a user control which has a chart to display employee statistics over a period of time. I have used MSChart. I have 3 different series and i want to switch between them at runtime so that the user has an option to view different statistics. I have used legenditem and using it's postback value, I have parsed it. I have put all of this in an UpdatePanel

The problem is that whenever I click on the legendItem, the control is reloaded and the Chart Area becomes blank. Here is my code. Please help me.

protected void Chart1_Click(object sender, ImageMapEventArgs e)
        {
            // If user clicks on the map area attribute that corresponds to a legend item
            if (e.PostBackValue.StartsWith("LegendClick"))
            {
                string args = e.PostBackValue.Split('/')[1];
                // Identify which legend item was clicked
                int index = int.Parse(args);

                // Legend item result
                LegendItem legendItem = this.Chart1.Legends[0].CustomItems[index];

                // Resets all radio button images to be unchecked
                /* foreach (LegendItem item in this.Chart1.Legends[0].CustomItems)
                 {
                     item.Cells[0].ImageTransparentColor = Color.Black;
                     item.Cells[0].Image = "radio_button_unchecked.gif";
                 }
                 */
                for (; ; )
                {

                    switch (legendItem.Cells[1].Text)
                    {
                        case "Points":
                            this.Chart1.Series["series1"].Enabled = true;
                            this.Chart1.Series["series2"].Enabled = false;
                            this.Chart1.Series["series3"].Enabled = false;
                            this.Chart1.Series[0].ChartType = (SeriesChartType)Enum.Parse(typeof(SeriesChartType), "Line", true);
                            this.Chart1.Legends[0].CustomItems[0].Cells[0].Image = "radio_button_checked.gif";
                            break;

                        case "CSAT":
                            this.Chart1.Series["series1"].Enabled = false;
                            this.Chart1.Series["series2"].Enabled = true;
                            this.Chart1.Series["series3"].Enabled = false;
                            this.Chart1.Legends[0].CustomItems[1].Cells[0].Image = "radio_button_checked.gif";
                            break;

                        case "SLA":
                            this.Chart1.Series["series1"].Enabled = false;
                            this.Chart1.Series["series2"].Enabled = false; ;
                            this.Chart1.Series["series3"].Enabled = true;
                            this.Chart1.Legends[0].CustomItems[2].Cells[0].Image = "radio_button_checked.gif";
                            break;

                    }
                }