MainPage.xaml.cs

private Image CreateCell()
{
    var cell = new Image();
    cell.Tapped += OnCellTapped;
    return cell;
}

private void OnCellTapped(object sender, Windows.UI.Xaml.Input.TappedRoutedEventArgs e)
{
    var index = _cells.IndexOf((Image)sender);

    int row = index / _gameState.Size;
    int column = index % _gameState.Size;

    _gameState.Cells[row, column] = _gameState.Cells[row, column] == CellState.Alive ?
            CellState.Dead : CellState.Alive;
    RedrawBoard();
}