c# asp.net youtube video downloader script

Update on 9/04/2010: Since youtube changed their layout code below may not work. Reason for that is that Youtube now generates unique machine id for each computer that visits it.

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Below code enables you to download youtube videos in MP4 format. It is easy to use
Save the code as youtube.aspx and call it like youtube.aspc?youtube=http://uk.youtube.com/watch?v=DD-pfi6vtnk&fmt=13

fmt 13 = 3GP download
fmt 18 = MP4 download

protected void Page_Load(object sender, EventArgs e)
    {

	        string vid_format = Request.QueryString["fmt"];
            if (vid_format == null)
            { vid_format = "13"; }


        if (Request.QueryString["youtube"] != null)
        {
            if (Request.QueryString["youtube"].ToString().Trim() != "")
            {
                string url = Request.QueryString["youtube"].ToString().Trim();
                url = convert(url);
                if (url != "")
                {
                    youtubecatch2(url,vid_format);
                }
            }
        }
    }


    private void youtubecatch2(string url, string vid_format)
    {
        string buffer = getContent(url);
        if (buffer.IndexOf("Error:") < 0)
        {
            try
            {

                int start = 0, end = 0;
                string startTag = "/watch_fullscreen?";
                string endTag = ";";
                start = buffer.IndexOf(startTag, StringComparison.CurrentCultureIgnoreCase);
                end = buffer.IndexOf(endTag, start, StringComparison.CurrentCultureIgnoreCase);
                string str = buffer.Substring(start + startTag.Length, end - (start + startTag.Length));
                string vid = str.Substring(str.IndexOf("video_id"), str.IndexOf("&", str.IndexOf("video_id")) - str.IndexOf("video_id"));
                string l = str.Substring(str.IndexOf("&l"), str.IndexOf("&", str.IndexOf("&l") + 1) - str.IndexOf("&l"));
                string t = str.Substring(str.IndexOf("&t"), str.IndexOf("&", str.IndexOf("&t") + 1) - str.IndexOf("&t"));
                string title = str.Substring(str.IndexOf("&title=") + 7);
                //title = title.Substring(0, title.Length - 1);
                //litResult.Text = "Download " + title + "";

                //Response.Redirect("http://youtube.com/get_video?" + vid + l + t +"&fmt=" + vid_format );
                Response.Redirect(GetRedirectedUrl("http://youtube.com/get_video?" + vid + l + t + "&fmt=" + vid_format));
                
				//Response.Write(buffer);



            }
            catch (Exception expTwo)
            {
			//Response.Write (expTwo.Message.ToString());
			//Response.Redirect("/removed.asp?err=1" /* + expTwo.Message.ToString())*/); 
			}
            
        }
        else
        {
            Response.Write (buffer); 
        }
    }
    private string GetRedirectedUrl(string url)
    {
        string buffer;
        try
        {
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
            req.Method = "GET";
            //req.ContentLength = outputBuffer.Length;
            //req.ContentType = "application/x-www-form-urlencoded";
            //StreamWriter swOut = new StreamWriter(req.GetRequestStream());
            //swOut.Write(outputBuffer);
            //swOut.Close();
            HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
            //StreamReader sr = new StreamReader(resp.GetResponseStream());
            //buffer = sr.ReadToEnd();
            //sr.Close();
            buffer = resp.ResponseUri.ToString();
        }
        catch (Exception exp)
        {
            buffer = "Error: " + exp.Message.ToString();
        }

        return (buffer);
    }
    

    private string getContent(string url)
    {
        string buffer;
        try
        {
            string outputBuffer = "where=46038";
            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
            req.Method = "POST";
            req.ContentLength = outputBuffer.Length;
            req.ContentType = "application/x-www-form-urlencoded";
            StreamWriter swOut = new StreamWriter(req.GetRequestStream());
            swOut.Write(outputBuffer);
            swOut.Close();
            HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
            StreamReader sr = new StreamReader(resp.GetResponseStream());
            buffer = sr.ReadToEnd();
            sr.Close();
        }
        catch (Exception exp)
        {
            buffer = "Error: " + exp.Message.ToString();
        }

        return (buffer);
    }
    private string convert(string url)
    {
        url = url.Replace("www.youtube.com", "youtube.com");
        if (url.IndexOf("http://youtube.com/v/") >= 0)
        {
            url.Replace("http://youtube.com/v/", "http://youtube.com/watch?v=");
        }
        if (url.IndexOf("http://youtube.com/watch?v=") < 0)
        {
            url = "";
        }
        return (url);
    }