Export multiple gridview is not working in different excel sheet using different button

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C#3.5

i want to export two gridview in different excel sheet using two different button in c#

protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack)
   {
      ScriptManager scriptManager = ScriptManager.GetCurrent(this.Page);
      scriptManager.RegisterPostBackControl(this.btnextract);

      ScriptManager scriptManager1 = ScriptManager.GetCurrent(this.Page);
      scriptManager1.RegisterPostBackControl(this.btnpostsap);
   }


   protected void btnextract_Click(object sender, EventArgs e)
   {
      if(btnextract.Text == "Extract Data")
      {
         Response.ClearContent();
         Response.Buffer = true;
         Response.AddHeader("content-disposition", string.Format("attachment; filename={0}", "Distribution.xls"));
         Response.ContentType = "application/ms-excel";
         System.IO.StringWriter sw = new System.IO.StringWriter();
         HtmlTextWriter htw = new HtmlTextWriter(sw);
         gridview1.AllowPaging = false;
         gridview1.HeaderRow.Font.Bold = true;
         gridview1.HeaderRow.Height = 25;
         gridview1.Columns[0].Visible = false;
         gridview1.RenderControl(htw);
         Response.Write(sw.ToString());
         Response.End();
      }
   }

   protected void btnpostsap_Click(object sender, EventArgs e)
   {
      if(btnpostsap.Text == "Sync Data")
      {
         Response.ClearContent();
         Response.Buffer = true;
         Response.AddHeader("content-disposition", 
         string.Format("attachment; filename={0}", "SyncSapData.xls"));
         Response.ContentType = "application/ms-excel";
         System.IO.StringWriter sw1 = new System.IO.StringWriter();
         HtmlTextWriter htw1 = new HtmlTextWriter(sw1);
         gridview2.AllowPaging = false;
         gridview2.Visible = true;
         gridview2.RenderControl(htw1);
         Response.Write(sw1.ToString());
         Response.End();
      }
   }

   public override void VerifyRenderingInServerForm(Control control)
   {
      /*Tell the compiler that the control is rendered
	explicitly by overriding the VerifyRenderingInServerForm event.*/
   }

i have two button as follows Extract Data and Sync Data.

when i click Extract data button Gridview1 is downloading. But when i click the Sync Data button Gridview2 is not downloading.

what is the mistake in my above postsap click button code.

What I have tried:

[EDIT] copy paste of previous text and code deleted to increase readability[/Edit]