Beauty_Salon/BeautySalon/BeautySalonDBModels/Implements/ClientDatabase.cs

using BeautySalonDBModels.Models;
using Npgsql;

namespace BeautySalonDBModels.Implements
{
    public class ClientDatabase : AbstractWorkWithStorage<Client>
    {
        public override void Add(Client client)
        {
            using var conn = GetConnection();
            conn.Open();
            using var cmd = new NpgsqlCommand("INSERT INTO clients (client_id, fio, age) VALUES ((nextval('seq_client')), @FIO, @Age)", conn);
            cmd.Parameters.AddWithValue("@FIO", client.FIO);
            cmd.Parameters.AddWithValue("@Age", client.Age);
            cmd.ExecuteNonQuery();
        }

        public override Client? GetObject(int id)
        {
            using var conn = GetConnection();
            conn.Open();
            using var cmd = new NpgsqlCommand("SELECT * FROM clients WHERE client_id = @id", conn);
            cmd.Parameters.AddWithValue("@id", id);
            using var reader = cmd.ExecuteReader();
            if (reader.Read())
            {
                return new Client
                {
                    ClientId = reader.GetInt32(0),
                    FIO = reader.GetString(1),
                    Age = reader.GetInt32(2)
                };
            }
            return null;
        }

        public override List<Client> GetObjects()
        {
            var clients = new List<Client>();
            using var conn = GetConnection();
            conn.Open();
            using var cmd = new NpgsqlCommand("SELECT * FROM clients order by client_id", conn);
            using var reader = cmd.ExecuteReader();
            while (reader.Read())
            {
                clients.Add(new Client
                {
                    ClientId = reader.GetInt32(0),
                    FIO = reader.GetString(1),
                    Age = reader.GetInt32(2)
                });
            }
            return clients;
        }

        public override Client? Remove(int id)
        {
            var client = GetObject(id);
            using var conn = GetConnection();
            conn.Open();
            using var cmd = new NpgsqlCommand("delete from clients where client_id = @id", conn);
            cmd.Parameters.AddWithValue("@id", id);
            cmd.ExecuteNonQuery();
            return client;
        }

        public override void Update(Client client)
        {
            using var conn = GetConnection();
            conn.Open();
            using var cmd = new NpgsqlCommand("update clients set fio = @FIO, " +
                "age = @Age where client_id = @ClientId", conn);
            cmd.Parameters.AddWithValue("@FIO", client.FIO);
            cmd.Parameters.AddWithValue("@Age", client.Age);
            cmd.Parameters.AddWithValue("@ClientId", client.ClientId);
            cmd.ExecuteNonQuery();
        }
    }
}