TicTactics GameBoard Logic

This is my take at the current code-challenge, Ultimate Tic-Tac-Toe.

It all started with a CellValue and a BoardPosition:

/// 
/// Identifies the players, or the possible values a cell can take.
/// 
public enum CellValue
{
    X,
    O
}

/// 
/// Identifies the possible board positions.
/// 
public enum BoardPosition
{
    TopLeft,
    Top,
    TopRight,
    Left,
    Center,
    Right,
    BottomLeft,
    Bottom,
    BottomRight
}

"Wait", I hear you say - "an enum for board positions?" - Absolutely! That allowed me to define a BoardCell interface:

public interface IBoardCell
{
    BoardPosition Position { get; }
    CellValue? Value { get; set; }
    event EventHandler CellValueChanged;
}

Inspired by WPF and INotifyPropertyChanged, I'm using events to communicate a change of a cell's value to whoever might be interested (that's the parent board):

public class CellValueChangedEventArgs : EventArgs
{
    private BoardPosition _position;
    BoardPosition Position { get { return _position; } }

    private CellValue? _value;
    CellValue? Value { get { return _value; } }

    public CellValueChangedEventArgs(BoardPosition position, CellValue? value)
    {
        _position = position;
        _value = value;
    }
}

BoardBase[TCell]

Very early in the design process I realized most of the "bigger board" functionality was also needed in the "smaller boards", so I wrote a generic abstract class where the type parameter determines the type of cell:

```
public abstract class BoardBase : IBoardCell
where TCell : IBoardCell
{
private readonly IDictionary _cells;
private readonly BoardEvaluator _evaluator;

protected BoardBase(BoardEvaluator evaluator, ICellFactory cellFactory)
{
_evaluator = evaluator;
_cells = Enum.GetValues(typeof(BoardPosition))
.Cast()
.ToDictionary(position => position, position => cellFactory.Create(position));
RegisterCellE

I like it,

especially the enums.

Although the Tuple evaluator is super hard to parse.

Definitely think it would be better to wrap that in a WinCondition interface or something which contains the relevant enum flag.

besides if memory serves you can perform flag concatenation for a cleaner compare.

BoardPosition winPosition = BoardPosition.TopLeft | BoardPosition.Top | BoardPosition.TopRight;

and make a list of them:

_winPositions.Any(position => position == currentPosition)

or something....

StackExchange Code Review Q#41029, answer score: 4