export gridview data using asp .net C#

public override void VerifyRenderingInServerForm(Control control)
    {
        /* Verifies that the control is rendered */
    }
    private void ExportPostExcelSheet(GridView gvDetails, string FileName)
    {
        try
        {
            Response.ClearContent();
            Response.Buffer = true;
            Response.AddHeader("content-disposition", string.Format("attachment; filename={0}", FileName));// "Customers.xls"
            Response.ContentType = "application/ms-excel";
            StringWriter sw = new StringWriter();
            HtmlTextWriter htw = new HtmlTextWriter(sw);
            gvDetails.AllowPaging = false;
            // BindGridview();
            //Change the Header Row back to white color
            gvDetails.HeaderRow.Style.Add("background-color", "#FFFFFF");
            //Applying stlye to gridview header cells
            for (int i = 0; i < gvDetails.HeaderRow.Cells.Count; i++)
            {
                gvDetails.HeaderRow.Cells[i].Style.Add("background-color", "#df5015");
            }
            gvDetails.RenderControl(htw);
            Response.Write(sw.ToString());
            Response.End();
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }