flutterfire where and orderby not return data - flutter

Question

i have implemented this code for retrieving the messages of this room.
final messagesProvider = StreamProvider((ref) {
FirebaseFirestore db = FirebaseFirestore.instance;
var room = ref.watch(roomIdProvider);
print('room updated');
print('room is '+room);
final docRef = db
.collection("messages")
.where("chat_room_id",isEqualTo: room)
// .orderBy('created_at')
// .orderBy('created_at',descending: true)
;
print(docRef.orderBy("created_at").snapshots());
return docRef.snapshots();
});
i want to sort the data and have tried these two lines separately but not worked for me
.orderBy('created_at')
.orderBy('created_at',descending: true)
where created at is a timestamp field.

Answer 1

I added a new collection called "school", there're two items added inside the document.
I used my code, and it works. Could you please remove ".where" and try it again?
void getMessagesTest() async{
QuerySnapshot querySnapshot = await _firestore.collection('school').orderBy('age',descending: true).get();
final allData = querySnapshot.docs.map((doc) => doc.data()).toList();
print(allData);
}
Updated 20220616:
Updated 20220618:
Yes, you could chain where and orderBy together. Please see my code below.
Reference link => Using Where and Order by different fields in Firestore query
void getMessagesTest() async{
QuerySnapshot querySnapshot = await _firestore.collection('school').orderBy('age', descending: true).where('age', isGreaterThan: 17).get();
final allData = querySnapshot.docs.map((doc) => doc.data()).toList();
print(allData);
}