memo

ようつべDL　C#
todo
public static string GetVideoUrl( string videoID ) {
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create( "http://www.youtube.com/watch?v=" + videoID );

HttpWebResponse res = (HttpWebResponse)req.GetResponse();
string result = new StreamReader( res.GetResponseStream() ).ReadToEnd();

int start = result.IndexOf( "url_encoded_fmt_stream_map=url%3D" ) + "url_encoded_fmt_stream_map=url%3D".Length;
int end = result.IndexOf( "%26quality" );
int length = end - start;
var source = result.Substring( start, length );
return Uri.UnescapeDataString(Uri.UnescapeDataString( source ));
}