从WebResponse获取源文件名、扩展名

        static string GetFilenameFromResponse(WebResponse wr, string defaultFilename)
        {

            string desc = wr.Headers["Content-Disposition"];

            if (desc != null)
            {
                string fstr = "filename=";
                int pos1 = desc.IndexOf(fstr);
                if (pos1 > 0)
                {
                    string fn = desc.Substring(pos1 + fstr.Length);
                    if (fn != "")
                        defaultFilename = System.Environment.CurrentDirectory + "\\" + fn;

                }

            }
            return defaultFilename;
        }

        static string GetExtensionFromResponse(WebResponse wr,string defaultExt)
        {
            Hashtable htmimes = new Hashtable();
            htmimes["image/jpeg"] = ".jpg";
            htmimes["image/png"] = ".png";
            htmimes["image/tiff"] = ".tif";
            htmimes["image/bmp"] = ".bmp";
            htmimes["image/gif"] = ".gif";

            string ct = wr.ContentType;
            if (ct != null)
            {
                if (htmimes.ContainsKey(ct)) defaultExt = htmimes[ct].ToString();
            }
            return defaultExt;
        }