//1.在Page_Load中添加Chart1的Click事件,索引每个点:
 protected void Page_Load(object sender, EventArgs e)
  {
       this.Chart1.Click += new ImageMapEventHandler(Chart1_Click);
       foreach (Series series in this.Chart1.Series)
       {
           series.PostBackValue = series.Name + ",#INDEX";
       }
  }

//2.在Chart1的Click事件下获得点击了第几个点!(加一个Label来显示演示)
  protected void Chart1_Click(object sender, ImageMapEventArgs e)
  {
        string[] input = e.PostBackValue.Split(',');
        Label1.Text = "你选中了" + input[0] + "的第 " + (Convert.ToInt16(input[1]) + 1).ToString() + " 点";

  }