/** Serializes info returned by NavGraph.SerializeExtraInfo */
static byte[] SerializeGraphExtraInfo (NavGraph graph) {
var stream = new MemoryStream();
var wr = new BinaryWriter(stream);
var ctx = new GraphSerializationContext(wr);
graph.SerializeExtraInfo(ctx);
byte[] bytes = stream.ToArray();
#if NETFX_CORE
wr.Dispose();
#else
wr.Close();
#endif
return bytes;
}