diff --git a/SUBD_Car_rent/database/ImplementationMongoDB.cs b/SUBD_Car_rent/database/ImplementationMongoDB.cs
index 2d8a380..7b549f6 100644
--- a/SUBD_Car_rent/database/ImplementationMongoDB.cs
+++ b/SUBD_Car_rent/database/ImplementationMongoDB.cs
@@ -12,6 +12,12 @@ namespace database
 		private IMongoCollection<Branch> _branchCollection;
 		private IMongoCollection<Status> _statusCollection;
 		private IMongoCollection<BodyType> _bodyTypeCollection;
+		private class Sequence
+		{
+			public string Id;
+			public int count;
+		}
+		private IMongoCollection<Sequence> _sequenceCollection;
 
 		public ImplementationMongoDB()
 		{
@@ -32,6 +38,13 @@ namespace database
 		// Car
 		public override void AddCar(Car car)
 		{
+			if (car.Id == 0)
+			{
+				Sequence sequence = _sequenceCollection.Find(seq => seq.Id == "car").FirstOrDefault();
+				sequence.count++;
+				car.Id = sequence.count;
+				_sequenceCollection.ReplaceOne(seq => seq.Id == "car", sequence);
+			}
 			_carCollection.InsertOne(car);
 		}
 
@@ -58,6 +71,13 @@ namespace database
 		// Client
 		public override void AddClient(Client client)
 		{
+			if (client.Id == 0)
+			{
+				Sequence sequence = _sequenceCollection.Find(seq => seq.Id == "client").FirstOrDefault();
+				sequence.count++;
+				client.Id = sequence.count;
+				_sequenceCollection.ReplaceOne(seq => seq.Id == "client", sequence);
+			}
 			_clientCollection.InsertOne(client);
 		}
 
@@ -84,6 +104,13 @@ namespace database
 		// Rental
 		public override void AddRental(Rental rental)
 		{
+			if (rental.Id == 0)
+			{
+				Sequence sequence = _sequenceCollection.Find(seq => seq.Id == "rental").FirstOrDefault();
+				sequence.count++;
+				rental.Id = sequence.count;
+				_sequenceCollection.ReplaceOne(seq => seq.Id == "rental", sequence);
+			}
 			_rentalCollection.InsertOne(rental);
 		}
 
@@ -110,6 +137,13 @@ namespace database
 		// CarModel
 		public override void AddCarModel(CarModel carModel)
 		{
+			if (carModel.Id == 0)
+			{
+				Sequence sequence = _sequenceCollection.Find(seq => seq.Id == "car_model").FirstOrDefault();
+				sequence.count++;
+				carModel.Id = sequence.count;
+				_sequenceCollection.ReplaceOne(seq => seq.Id == "car_model", sequence);
+			}
 			_carModelCollection.InsertOne(carModel);
 		}
 
@@ -136,6 +170,13 @@ namespace database
 		// Branch
 		public override void AddBranch(Branch branch)
 		{
+			if (branch.Id == 0)
+			{
+				Sequence sequence = _sequenceCollection.Find(seq => seq.Id == "branch").FirstOrDefault();
+				sequence.count++;
+				branch.Id = sequence.count;
+				_sequenceCollection.ReplaceOne(seq => seq.Id == "branch", sequence);
+			}
 			_branchCollection.InsertOne(branch);
 		}