Hi franco, you code really works . thank you for that. I would like to share some of other option when using AJAX since responce.write() cannot be use.
string script = "<script language=\"Javascript\">\n";
script += "window.open('download.aspx')\n";
script += "</script>";
this.ClientScript.RegisterStartupScript(this.GetType(), "onload", script);
Roses are #FF0000 Violets are #0000FF all my base are belong to you