public class GameBoardCell : TextBox
  {
    public bool IsBlocked;
    protected SudokuControl _Mother;
    protected int _Value;
    public int Value
    {
      get { return _Value; }
    }
    protected List<int> _PossibleValues;
    public GameBoardCell(SudokuControl Mother)
    {
      _Value = 0;
      _Mother = Mother;
    }
    public void SetPossibleValues(List<int> possibles)
    {
      _PossibleValues = possibles;
      _Value = _PossibleValues[0];
      _PossibleValues.RemoveAt(0);
      this.Text = _Value.ToString();
    }
    public bool StepNextPossibleEntry()
    {
      if (IsBlocked == true) return false;
      if (_PossibleValues.Count > 0)
      {
        _Value = _PossibleValues[0];
        _PossibleValues.RemoveAt(0);
        this.Text = _Value.ToString();
        return true;
      }
      _Value = 0;
      return false;
    }
    protected override void OnTextChanged(EventArgs e)
    {
      _Value = Int16.Parse(this.Text);
      if (_Mother.IsInEditMode == true)
        IsBlocked = true;
      base.OnTextChanged(e);
    }
}