ASP page freezes after export functionality

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ASP.NET

C#5.0

SharePoint2013

Hi,

I have a set of asp controls in my web page as below

<asp:DropDownList ID="ddlScope" runat="server" CssClass="combobox noMarginBottom marginRight10 floatLeft"></asp:DropDownList>
                            <asp:Button ID="btnApplyfilter" runat="server" Text="Apply Filter" OnClick="BtnApplyfilter_Click" CssClass="submitBtn floatLeft marginRight10 marginLeft10" />
                            <asp:Button ID="btnClearfilter" runat="server" Text="Clear Filter" OnClick="BtnClearfilter_Click" CssClass="submitBtn floatLeft marginRight10" />
                            <asp:Button ID="btnExport" runat="server" Text="Export" OnClick="BtnExport_Click" CssClass="submitBtn floatLeft marginRight10" />      

When i click each and every button there is a page submit. It all works fine until we click the export button. When we click the export button we are exporting some data to excel using the code below

var response = Context.Response;
               response.Clear();
               response.ClearHeaders();
               response.ClearContent();
               response.AddHeader("Content-Disposition", string.Concat("attachment; filename=Data_", string.Format("{0:yyyyMMdd_hhmmsstt}", DateTime.Now), ".xlsx"));
               response.AddHeader("Content-Length", buffer.Length.ToString());
               response.ContentType = "application/vnd.ms-excel";
               response.Flush();
               response.BinaryWrite(buffer);
               response.End();

But after the file are exported the page just freezes. All buttons clicks wont work.

Can anyone please help me out.

Thanks
Arjun Menon