My dropdown won't work after I exported the gridview to excel file?

Question

I have a dropdown called company and a button called export to excel and a gridview, also I have an update panel for both controls but when I export to excel dropdown won't work anymore, even if a want to export 2times I cannot without refreshing the page.

My export code:

   protected void Button1_Click(object sender, EventArgs e)
   {

      // HttpContext.Current.Response.Clear();
       HttpContext.Current.Response.AddHeader(
           "content-disposition", string.Format("attachment; filename={0}", "Kontratat-" + DateTime.Now.ToShortDateString() + ".xls"));
       HttpContext.Current.Response.ContentType = "application/vnd.ms-excel";


       StringWriter sw = new StringWriter();
       HtmlTextWriter hw = new HtmlTextWriter(sw);


       HtmlForm frm = new HtmlForm();
       hw.WriteLine("<center><b><u><font size='5'>Kontratat</font></u></b></center>");//will be displayed in excel as a heading.
       GridView1.Parent.Controls.Add(frm);
       frm.Controls.Add(GridView1);
       frm.RenderControl(hw);
       HttpContext.Current.Response.Write(sw.ToString());
       HttpContext.Current.Response.Flush();
       HttpContext.Current.Response.End();

   }            

and my aspx code

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<Triggers>
    <asp:AsyncPostBackTrigger ControlID="DropDownList1" EventName="SelectedIndexChanged" />
   <asp:PostBackTrigger ControlID="Button1" />
</Triggers>
<ContentTemplate>
    <asp:GridView ID="GridView1" runat="server" BackColor="#CCCCCC" BorderColor="#999999" BorderStyle="Solid" BorderWidth="1px" CellPadding="4" CellSpacing="2" ForeColor="Black">
    </asp:GridView>
</ContentTemplate>

help me please

Answer 1

Because you have called the Response.End(), which ends the page execution, the body onload event would never be fired. The problem is sharepoint catches form submits and downloads so you cannot double click a button.

I had same issue, adding below script on aspx page helped me to resolve it

<script type='text/javascript'>
    _spOriginalFormAction = document.forms[0].action;
    _spSuppressFormOnSubmitWrapper = true;
</script>

You can find reference here:

https://shenhengbin.wordpress.com/2012/03/16/cant-post-back-anything-after-file-download-in-sharepoint/

Refreshing page or making it to respond after downloading the file. All happening in Webpart

Answer 2

It is SharePoint which displays your value as a DropDown/Select. The Field value in the SQL database is stored as a String (with only the selected value).

When you export to Excel it exports values, not SharePoint functionality