Not Exporting Ajax ControlToolkit Linechart to excel asp.net

In my application i have Ajax Toolkit control linechart i need to  linechart to excel sheet(open office/Libra office). i tried some code in export button but what happens line chart is not export to excel.what i need is chart should be export to excel. how to do this.

 I am using one method OnPreRender()

I tried code is:

protected void btnExport_Click(object sender, EventArgs e)
{
Response.ClearContent(); 
Response.Buffer = true;
Response.AddHeader("content-disposition", string.Format("attachment; filename={0}", "filename.xls"));
Response.ContentType = "application/ms-excel"; 
StringWriter sw = new StringWriter(); 
HtmlTextWriter htw = new HtmlTextWriter(sw);
 base.OnPreRender(e); 
ScriptManager sm = ScriptManager.GetCurrent(Page);    
sm.RegisterScriptControl(LineChart1);
LineChart1.Visible = true; 
for (int i = 0; i < grdview1.HeaderRow.Cells.Count; i++)
{
grdview1.HeaderRow.Cells[i];
 }        
grdview1.RenderControl(htw); 
LineChart1.RenderControl(htw); 
Response.Write(sw.ToString()); 
Response.End();
 }  
public override void VerifyRenderingInServerForm(Control control) 
{ /* Verifies that the control is rendered */
 }

protected override void OnPreRender(EventArgs e) 
{
 /* Verifies that the control is rendered */
 base.OnPreRender(e); 
ScriptManager scriptManager = ScriptManager.GetCurrent(this.Page);
 if (scriptManager == null) 
{              
scriptManager = new ScriptManager();    
scriptManager.ID = "ScriptManager1";     
scriptManager.EnablePartialRendering = true; 
Controls.AddAt(0, scriptManager);
 }
 }

can anyone tell me how to export Ajax Control Toolkit using line chart to excel
Thank you