Asp.Net Export to Excel

Protected Sub btnExport_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnExport.Click
       Response.Clear()
       Response.AddHeader("content-disposition", "attachment; filename=ABC.xls")
       Response.Charset = ""
       Response.ContentType = "application/vnd.xls"

       Dim FilePathName As String = Request.PhysicalPath
       Response.WriteFile(FilePathName, IO.FileMode.Open, IO.FileAccess.Read)
       Dim stringWrite As New System.IO.StringWriter()
       Dim htmlWrite As System.Web.UI.HtmlTextWriter = New HtmlTextWriter(stringWrite)

       GridView1.HeaderRow.Style.Add("background-color", "#99CCFF")
       GridView1.RenderControl(htmlWrite)
       Response.Write(stringWrite.ToString())

       Response.[End]()