kubsu-sm4-db-lab-win-forms/db_lab/EquipmentRepository.cs

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Npgsql;

namespace db_lab
{
    public class EquipmentRepository
    {
        private NpgsqlConnection connection;

        public EquipmentRepository(string connectionString)
        {
            this.connection = new NpgsqlConnection(connectionString);
        }

        public DataTable ReadEquipments(int pageSize, int pageNumber)
        {
            string query = $"SELECT * FROM Equipment ORDER BY id LIMIT {pageSize} OFFSET {(pageNumber - 1) * pageSize}";
            NpgsqlDataAdapter da = new NpgsqlDataAdapter(query, connection);
            DataTable dt = new DataTable();
            da.Fill(dt);
            return dt;
        }

        public void DeleteEquipment(int id)
        {
            string query = $"DELETE FROM Equipment WHERE id = {id}";
            using (var cmd = new NpgsqlCommand(query, connection))
            {
                connection.Open();
                cmd.ExecuteNonQuery();
                connection.Close();
            }
        }

        public void AddEquipment(string ipAddress, string sshSettings, string name, int roomId)
        {
            string query = "INSERT INTO Equipment (ip_address, ssh_settings, name, room_id) VALUES (@ip_address, @ssh_settings, @name, @room_id)";
            using (var cmd = new NpgsqlCommand(query, connection))
            {
                cmd.Parameters.AddWithValue("ip_address", ipAddress);
                cmd.Parameters.AddWithValue("ssh_settings", sshSettings ?? (object)DBNull.Value);
                cmd.Parameters.AddWithValue("name", name);
                cmd.Parameters.AddWithValue("room_id", roomId);

                connection.Open();
                cmd.ExecuteNonQuery();
                connection.Close();
            }
        }

        public void UpdateEquipment(int id, string ipAddress, string sshSettings, string name, int roomId)
        {
            string query = "UPDATE Equipment SET ip_address = @ip_address, ssh_settings = @ssh_settings, name = @name, room_id = @room_id WHERE id = @id";
            using (var cmd = new NpgsqlCommand(query, connection))
            {
                cmd.Parameters.AddWithValue("ip_address", ipAddress);
                cmd.Parameters.AddWithValue("ssh_settings", sshSettings ?? (object)DBNull.Value);
                cmd.Parameters.AddWithValue("name", name);
                cmd.Parameters.AddWithValue("room_id", roomId);
                cmd.Parameters.AddWithValue("id", id);

                connection.Open();
                cmd.ExecuteNonQuery();
                connection.Close();
            }
        }

        public DataRow GetEquipmentById(int id)
        {
            string query = $"SELECT * FROM Equipment WHERE id = {id}";
            NpgsqlDataAdapter da = new NpgsqlDataAdapter(query, connection);
            DataTable dt = new DataTable();
            da.Fill(dt);
            return dt.Rows.Count > 0 ? dt.Rows[0] : null;
        }
    }
}