GetHtmlImageMap returning an empty map element

Question

GetHtmlImageMap does not return any meaningfull HTML image map code. It returns and empty image map as shown below: 

string chart = GetChart(data);
chart.RenderType = RenderType.ImageMap;
string map = chart.GetHtmlImageMap("trendmap");

map returns the following:

<map name="trendmap">
    <area shape="rect" coords="0,0,0,0" alt=""/>
</map>

I have the following method block in my code

Chart GetChart(Tripple<string, decimal, decimal> data)
{
    Chart chart = new Chart();
    chart.IsMapEnabled = true;
    chart.Width = 600;
    chart.Height = 150; 

    // Populate series with random data
    Series series1 = new Series("Bank");
    Series series2 = new Series("Peer"); 

    for (int i; i < data.Count; i++)
    {
        series1.Points.AddXY(data[i].First, data[i].Second);
        series2.Points.AddXY(data[i].First, data[i].Third);

        series1.Points[i].ToolTip = string.Format("{0}: {1}", data[i].First, data[i].Second);
        series2.Points[i].ToolTip = string.Format("{0}: {1}", data[i].First, data[i].Third);
    }

    chart.Series.Add(series1);
    chart.Series.Add(series2);

Am I missing a property?

    return chart;
}

Answer 1

Call Chart.SaveImage( Stream.Null ) before Chart.GetHtmlImageMap;

string chart = GetChart(data);
chart.SaveImage( Stream.Null );
string map = chart.GetHtmlImageMap("trendmap");

Delian