public static GameResult GetGameResult(Mark[,] field)
{
    if (HasWinSequence(field,Mark.Cross) == HasWinSequence(field,Mark.Circle)) return GameResult.Draw;
    else if (HasWinSequence(field,Mark.Circle) == true) return GameResult.CircleWin;
	else if (HasWinSequence(field,Mark.Cross) == true) return GameResult.CrossWin;
    else return GameResult.Draw;
}

public static bool HasWinSequence(Mark[,] field, Mark mark)
{
		        // По горизонтали
           return(((field[0,0] == mark && field[1,0] == mark && field[2,0] == mark) ||
               (field[0,1] == mark && field[1,1] == mark && field[2,1] == mark) ||
               (field[0,2] == mark && field[1,2] == mark && field[2,2] == mark)) ||

               // По вертикали
               ((field[0,0] == mark && field[0,1] == mark && field[0,2] == mark) ||
               (field[1,0] == mark && field[1,1] == mark && field[1,2] == mark) ||
               (field[2,0] == mark && field[2,1] == mark && field[2,2] == mark)) ||

               // По диагонали
               ((field[0,0] == mark && field[1,1] == mark && field[2,2] == mark) ||
               (field[2,0] == mark && field[1,1] == mark && field[0,2] == mark)));

}