Exploded=true property of pie chart

Question

Hi,
Currently I am using MS pieChart for creating a graph making use of my sql database values
I am able to show a proper pie chart
But I am unable to make use of Exploded=true property

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For example
code:
Chart1.Series["Series1"].PostBackValue = "#INDEX";
..............
protected void Chart1_Click(object sender, ImageMapEventArgs e)
{
int pointIndex = int.Parse(e.PostBackValue);
.........
..........
}
.............

here pointindex shows the currently clicked slice(portion of pie chart)

both Series1["CollectedSliceExploded"]= "true"; and
Chart1.Series["Series1"].Points[pointIndex].CustomProperties += "Exploded=true"; are not giving the expected
Because, through code I am unable to identify total number of slices.(I think,this is the problem)
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aspx page:

<asp:Chart ID="Chart1" runat="server" DataSourceID="SqlDataSource1" onclick="Chart1_Click">
<Series>
<asp:Series ChartType="Pie" Name="Series1" XValueMember="Day" YValueMembers="EmpNo">
.......

<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:EmployeeConnectionString1 %>"
SelectCommand="SELECT [Day], [EmpNo] FROM [EmployeeWorkChart]">
</asp:SqlDataSource>

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I tried the same with hard coded values instead of taking it from database...Then it works
(ie hard coding the values to yValues&xValues)

double[] yValues = {.... }
string[] xValues = {.......}

Chart1.Series["Series1"].PostBackValue = "#INDEX";
series.Points.DataBindY(yValues);
.............................
protected void Chart1_Click(object sender, ImageMapEventArgs e)
    {    
        int pointIndex = int.Parse(e.PostBackValue);
        Series series = Chart1.Series["My series"];
            if (pointIndex >= 0 && pointIndex <= series.Points.Count)
                {
                  series.Points[pointIndex].CustomProperties += "Exploded=true";
                  }
    } 
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How can I do the same without hardcoding the values

Expecting reply
Thanks in Advance
               Basanth