Export .dbf file from dataset

Response.Clear()
            Response.AddHeader("content-disposition", "attachment;filename=" + FileName + typefile)
            Response.Charset = ""
            Response.Cache.SetCacheability(HttpCacheability.Public)
            Response.ContentType = "application/vnd" + typefile
            Dim stringWrite As New System.IO.StringWriter()
            Dim htmlWrite As System.Web.UI.HtmlTextWriter = New HtmlTextWriter(stringWrite)
            gvExport.RenderControl(htmlWrite)
            Response.Write(stringWrite.ToString())
            Response.End()