private void goBack_Click(object sender, RoutedEventArgs e)
        {
            Person osoba = new Person();

            osoba.email     = "Guest";
            osoba.id_person = "0";
            ShopMain page = new ShopMain(osoba);

            page.Show();
            this.Close();
        }
        private void Login()
        {
            var client  = new RestClient("https://student.sps-prosek.cz/~bastlma14/obj/account.php");
            var request = new RestRequest(Method.POST);

            request.AddParameter("action", 0);
            request.AddParameter("email", Email.Text);
            request.AddParameter("password", Password.Password);
            var res = client.Execute <List <Person> >(request);

            if (res.Content == "0" || res.Content == "")
            {
                Error.Content = "Neznámé heslo nebo email";
            }
            else
            {
                Person osoba = new Person();
                osoba.email     = Email.Text;
                osoba.id_person = res.Content;
                ShopMain page = new ShopMain(osoba);
                page.Show();
                this.Close();
            }
        }