private void AddAccount_Click(object sender, RoutedEventArgs e)
{
if (LoginTextBox.Text.Length < 4 || PasswordTextBox.Text.Length < 4)
{
MessageBox.Show("Login and password should have at least 4 symbols.", "Error", MessageBoxButton.OK, MessageBoxImage.Error);
return;
}
AccountsList.ItemsSource = _engine.AddAccount(LoginTextBox.Text, PasswordTextBox.Text);
LoginTextBox.Text = "";
PasswordTextBox.Text = "";
}