Asp.net Chart Control逐渐消失

Question

我在一个aspx页面上有四个图表控件。单击一个图表下一个图表将出现，因此我已经绑定了点击事件上的所有图表。但是在第三张图表的点击事件中，第一张图表正在消失。所有其他点击事件都正常。以下是提到的代码：

protected void Chart3_Click(object sender, ImageMapEventArgs e)
{
    string pointData = e.PostBackValue.Split(';')[0];

    Session["pointvalue2"] = pointData;
    BindChart1();
    bindchart2();
    BindChart3();
    bindchart4();
}

  public void BindChart1()
    {

         DateTime fromdate = Convert.ToDateTime(txtfromdate.Text);


        string sqlFormattedDate = fromdate.ToString("yyyy-MM-dd HH:mm:ss.fff");
        Session["fromdate"] = sqlFormattedDate;



        DateTime todate = Convert.ToDateTime(txttodate.Text);
        string sqlFormattedDate1 = todate.ToString("yyyy-MM-dd HH:mm:ss.fff");

        Chart1.Visible = true;
        string constr = ConfigurationManager.ConnectionStrings["conn"].ConnectionString;
        using (SqlConnection conn = new SqlConnection(constr))
        {
            conn.Open();
             SqlCommand cmd = new SqlCommand("select col2 as 'col2', col1 as 'col1',col3 as 'col3' from dbo.table where APPLICATION = 'test' and col1 BETWEEN @fromdate AND @todate group by MONTH(col1),col2", conn);


            cmd.Parameters.AddWithValue("@fromdate", sqlFormattedDate);
            cmd.Parameters.AddWithValue("@todate", sqlFormattedDate1);
                           cmd.CommandType = CommandType.Text;

            SqlDataReader rdr = cmd.ExecuteReader();
            gvreport.DataSource = rdr;
            gvreport.DataBind();


        }
        DataTable dt = new DataTable();
        dt.Columns.Add(new DataColumn("severity", typeof(string)));
        dt.Columns.Add(new DataColumn("Count", typeof(int)));
        dt.Columns.Add(new DataColumn("Time", typeof(int)));

        foreach (GridViewRow row in gvreport.Rows)
        {
            DataRow dr = dt.NewRow();
            dr["Count"] = Convert.ToInt32(row.Cells[0].Text);
            dr["severity"] = row.Cells[1].Text;
            dt.Rows.Add(dr);
        }
        DataTable ChartData = dt;
        Chart1.DataSource = dt;
        Session["dtTest"] = dt;

        // Set series members names for the X and Y values
        Chart1.Series["Series1"].XValueMember = "severity";
        Chart1.Series["Series1"].YValueMembers = "Count";

        // Data bind to the selected data source
        Chart1.DataBind();
        Chart1.Titles.Add("Chart");
        Chart1.Series[0].ChartType = SeriesChartType.Pie;
        Chart1.Series["Series1"]["PieLabelStyle"] = "Disabled";
        Chart1.Series["Series1"].ToolTip = "Related_CI_Type: #VALX, Count: #VALY";
        foreach (Series series in Chart1.Series)
        {
            series.PostBackValue = "#SERIESNAME;#VALX;#VALY";
        }
        Chart1.Visible = true;

    }

请建议。在此先感谢。