when user clicked on pie chat slice how to store the value in sql database

code in .cs file

        // complete code of Visualization: Combo Chart
        SqlConnection con = new SqlConnection();
        // here am declairing the stringbuilder class
        StringBuilder str = new StringBuilder();
        SqlCommand cmd;
// here datatale dt is fill wit the adp
             adp.Fill(dt);
             // this string m catching in the stringbuilder class
             // in the str m writing same javascript code that is given by the google.

             str.Append(@"<script type=text/javascript>  google.load('visualization', '1', {'packages':['corechart']});
                  google.setOnLoadCallback(drawChart);
                  function drawChart() {
                  var data = new google.visualization.DataTable();");
             // but m changing  only below line
             // (" data.addColumn('string'(datatype), 'student_name'(column name));");
             // str.Append(" data.addColumn('number'(datatype), 'average_marks'(column name));");
             // my data that will come from the sql server
             str.Append(" data.addColumn('string', 'reward');");
             str.Append(" data.addColumn('number', 'SrNo');");
             str.Append(" data.addRows([");
             // here i am declairing the variable i in int32 for the looping statement
             Int32 i;
             // loop start from 0 and its end depend on the value inside dt.Rows.Count - 1
             for (i = 0; i <= dt.Rows.Count - 1; i++)
             {
                 // here i am fill the string builder with the value from the database
                 str.Append("['" + (dt.Rows[i]["reward"].ToString()) + "'," + dt.Rows[i]["SrNo"].ToString() + "],");
             }
             // other all string is fill according to the javascript code
             str.Append(" ]);");
             str.Append(" var chart = new google.visualization.PieChart(document.getElementById('chart_div'));");
             //  str.Append(" var chart = new google.visualization.BarChart(document.getElementById('chart_div'));");
             str.Append("chart.draw(data, {width: 1200, height: 500,title: 'Students Record'});}");
             str.Append("</script>");
             // here am using literal conrol to display the complete graph
             lt.Text = str.ToString().TrimEnd(',');
             con.Close();


code in .aspx

    <div>
        <asp:Literal ID="lt" runat="server"></asp:Literal>
    </div>
    <div id="chart_div">
    </div>