Click events for aps.net chart not working

I m working Asp.net chart and showing few data, i tried with default click even in chart and trying to debug. I m getting error as Error 1 No overload for 'Chart1_Click' matches delegate 'System.Web.UI.ImageClickEventHandler'

Below are codes. Please help me to fix the same.

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Chart1.Click += new ImageClickEventHandler(Chart1_Click);
...
..
}}

protected void Chart1_Click(object sender, ImageMapEventArgs e)
{
string s = e.PostBackValue;

}