Hermes/DataAccess.cs

using Microsoft.Data.Sqlite;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Policy;
using System.Text;
using System.Threading.Tasks;

namespace Hermes
{
    public static class DataAccess
    {
        private static SqliteConnection db= null;

        public static SqliteConnection GetConnection() {
            if (db != null) {
                return db;
            }

            var dbpath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "hermes.db");
            if (!System.IO.File.Exists(dbpath)) {
                FileStream fs = File.Create(dbpath);
                fs.Close();
            }
            db = new SqliteConnection($"Filename={dbpath}");
            db.Open();

            var createTableCmd = "CREATE TABLE IF NOT EXISTS citoyen (id INTEGER PRIMARY KEY, nom TEXT NOT NULL, prenom TEXT NOT NULL, date_naissance TEXT NOT NULL, adresse TEXT NOT NULL, profession TEXT, type_residence INTEGER NOT NULL, mail TEXT, tel TEXT)";

            SqliteCommand createTable = new SqliteCommand(createTableCmd, db);
            createTable.ExecuteReader();

            return db;
        }

        public static void CloseConnection() {
            if (db != null) {
                db.Close();
                db = null;
            }
        }
    }
}