asp.net 文件下载

   protected void down(string filePath)
    {
        Response.Buffer = true;
        Response.Clear();
        Response.ContentType = "application/octet-stream";
        Response.AddHeader("Content-Disposition", "attachment;FileName=" + HttpUtility.UrlEncode("MedusaSetUp.rar", Response.HeaderEncoding));
        FileStream fs = File.Open(filePath, FileMode.Open);
        byte[] ss = new byte[fs.Length];
        fs.Read(ss, 0, (int)fs.Length);
        fs.Close();
        Response.BinaryWrite(ss);
        Response.Flush();
        Response.End();
    }