public static List<User> getUsersByOrganization(int organization_id)
        {
            List<User> users = new List<User>();
            SqlConnection konekcija = getConnection();
            string sqlString = "SELECT * FROM Users WHERE organization_id=@organization_id and is_active=1";
            SqlCommand komanda = new SqlCommand(sqlString, konekcija);
            komanda.Parameters.AddWithValue("@organization_id", organization_id);
            try
            {
                konekcija.Open();
                SqlDataReader citac = komanda.ExecuteReader();
                while (citac.Read())
                {
                    User u = new User();
                    u.user_id = int.Parse(citac["user_id"].ToString());
                    u.first_name = citac["first_name"].ToString();
                    u.last_name = citac["last_name"].ToString();
                    u.organization_id = int.Parse(citac["organization_id"].ToString());
                    users.Add(u);
                }
            }
            catch (Exception err)
            {
                Console.Write(err.ToString());
            }
            finally
            {
                konekcija.Close();
            }

            return users;
        }
        public static User authenticateUser(string username, string password)
        {
            SqlConnection konekcija = getConnection();
            string sqlString = "SELECT * FROM Users WHERE username=@username AND password=@password AND is_active = 1";
            SqlCommand komanda = new SqlCommand(sqlString, konekcija);
            komanda.Parameters.AddWithValue("@username", username);
            komanda.Parameters.AddWithValue("@password", password);

            try
            {
                konekcija.Open();
                SqlDataReader citac = komanda.ExecuteReader();
                if (citac.Read())
                {

                    User u = new User();
                    u.user_id = int.Parse(citac["user_id"].ToString());
                    u.first_name = citac["first_name"].ToString();
                    u.last_name = citac["last_name"].ToString();
                    u.organization_id = int.Parse(citac["organization_id"].ToString());

                    return u;
                }
                else
                    return null;
            }
            catch (Exception err)
            {
                Console.Write(err.ToString());
            }
            finally
            {
                konekcija.Close();
            }
            return null;
        }
        public static User getUserByID(int id)
        {
            SqlConnection konekcija = getConnection();
            string sqlString = "SELECT u.*, o.organization_name FROM Users u, Organizations o WHERE u.user_id=@user_id AND u.organization_id=o.organization_id";
            SqlCommand komanda = new SqlCommand(sqlString, konekcija);
            komanda.Parameters.AddWithValue("@user_id", id);

            try
            {
                konekcija.Open();
                SqlDataReader citac = komanda.ExecuteReader();
                if (citac.Read())
                {

                    User u = new User();
                    u.user_id = int.Parse(citac["user_id"].ToString());
                    u.first_name = citac["first_name"].ToString();
                    u.last_name = citac["last_name"].ToString();
                    u.username = citac["username"].ToString();
                    u.gender = Convert.ToBoolean(citac["gender"].ToString());
                    u.birth_date = Convert.ToDateTime(citac["birth_date"].ToString());
                    u.organization_id = int.Parse(citac["organization_id"].ToString());
                    u.organization_name = citac["organization_name"].ToString();
                    u.join_date = Convert.ToDateTime(citac["join_date"].ToString());
                    u.location = citac["location"].ToString();
                    u.address = citac["address"].ToString();
                    u.phone = citac["phone"].ToString();
                    u.email = citac["email"].ToString();
                    u.image_path = citac["image_path"].ToString();
                    return u;
                }
                else
                    return null;
            }
            catch (Exception err)
            {
                Console.Write(err.ToString());
            }
            finally
            {
                konekcija.Close();
            }
            return null;
        }
        public static List<User> getAllUsers()
        {
            List<User> users = new List<User>();
            SqlConnection konekcija = getConnection();
            string sqlString = "SELECT u.*, o.organization_name FROM Users u, Organizations o WHERE o.organization_id = u.organization_id";
            SqlCommand komanda = new SqlCommand(sqlString, konekcija);

            try
            {
                konekcija.Open();
                SqlDataReader citac = komanda.ExecuteReader();
                while (citac.Read())
                {
                    User u = new User();
                    u.user_id = int.Parse(citac["user_id"].ToString());
                    u.first_name = citac["first_name"].ToString();
                    u.last_name = citac["last_name"].ToString();
                    u.organization_name = citac["organization_name"].ToString();
                    users.Add(u);
                }
            }
            catch (Exception err)
            {
                Console.Write(err.ToString());
            }
            finally
            {
                konekcija.Close();
            }

            return users;
        }