TicTacToe game in C#

Question

I have been studying C#, and I am trying to model the Tic Tac Toe game. Is my program reasonable or is there anything I need to improve?

 enum Result
{
 None,
 Win,
 Draw
}
public class TicTacToe
{
 static char[] board = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
 char player = 'O';
 Result result = Result.None;
 public void PlayGame()
 {
 Intro();
 do
 {
 Console.Clear();
 Console.WriteLine("Player 1 : O Player 2 : X");
 DrawBoard();
 Console.WriteLine($"\nPlayer {player}'s Turn \nPlease Enter the empty number");
 label:
 int choice = 0;
 while (!int.TryParse(Console.ReadLine(), out choice))
 {
 Console.WriteLine("Enter the num please");
 }
 if (choice >= 10)
 {
 Console.WriteLine("Please enter btw 1 - 9");
 goto label;
 }
 if (board[choice] != 'X' && board[choice] != 'O')
 {
 board[choice] = player;
 ChangeTurn();
 }
 CheckWin();
 } while (result != Result.Draw && result != Result.Win);
 Console.Clear();
 DrawBoard();
 GameResult();
 Console.ReadKey();
 }
 void ChangeTurn()
 {
 if (player == 'X')
 player = 'O';
 else if (player == 'O')
 player = 'X';
 }
 void GameResult()
 {
 if (result == Result.Win)
 {
 ChangeTurn();
 Console.WriteLine("Player {0} has won", player);
 }
 else if(result == Result.Draw)
 {
 Console.WriteLine("Draw");
 }
 Console.ReadLine();
 }
 void Intro()
 {
 Console.WriteLine("Welcome to TieTacToe");
 Console.WriteLine("Press any Key to continue");
 Console.ReadKey();
 Console.Clear();
 }
 void DrawBoard()
 {
 int x = 1;
 Console.WriteLine();
 for (int row = 0; row < 3; row++)
 {
 Console.Write("| ");
 for (int col = 0; col < 3; col++)
 {
 Console.Write(board[x]);
 Console.Write(" | ");
 x++;
 }
 Console.WriteLine();
 }
 } 
 void CheckWin()
 {
 // horzontial
 if (board[1] == board[2] && board[2] == board[3])
 {
 result = Result.Win;
 }
 else if (board[4] == board[5] && board[5] == board[6])
 {
 result = Result.Win;
 }
 else if (board[7] == board[8] && board[8] == board[9])
 {
 result = Result.Win;
 }
 // vertical
 else if (board[1] == board[4] && board[4] == board[7])
 {
 result = Result.Win;
 }
 else if (board[2] == board[5] && board[5] == board[8])
 {
 result = Result.Win;
 }
 else if (board[3] == board[6] && board[6] == board[9])
 {
 result = Result.Win;
 }
 // X
 else if (board[1] == board[5] && board[5] == board[9])
 {
 result = Result.Win;
 }
 else if (board[3] == board[5] && board[5] == board[7])
 {
 result = Result.Win;
 }
 else if (board[1] != '1' && board[2] != '2' && board[3] != '3' && board[4] != '4' && board[5] != '5' && board[6] != '6' && board[7] != '7' && board[8] != '8' && board[9] != '9')
 {
 result = Result.Draw;
 }
 else
 {
 result = Result.None;
 }
 }
}

Answer 1

If you want to be completely safe, I would also check the 'choice' to make sure that it was not a negative number.

Goto's should be avoided. You can easily refactor your code to use a while loop and break.

In your function GameResult(), I would use a switch statement instead of the if chain.

I am also thinking that CheckWin() might be a bit too cumbersome with all of the if statements and the checking of the individual cells. I might keep a "shadow board" behind the scenes, where a cell is 1 if it is an X and -1 if it is an O. Some simple addition and a test to see if the Math.Abs(sum) == 3 is an easy way to test for a win. For example:

if (Math.Abs(board[1] + board[2] + board[3]) == 3)
 result = Result.Win;

You can even refactor what I wrote above by keeping a list of the triplets to check.

Good luck with your studies of C#.

• user10443653: thank you for your helpful comments. One thing, I understand that CheckWin()is repeated too much with if statements. How can I keep "shadow board". If its not too much asking, could you show me?
• Marc Adler: The "shadow board" would be the exact same thing as your variable 'board', but it would just contain 3 values ... -1 for the letter O, 0 if the box has not been filled out, and 1 for the letter X. static int[] shadowBoard = new int[10]; When the user fills in the X or O, you also fill in the shadowBoard with the appropriate numeric value. board[choice] = player; shadowBoard[choice] = player == 'X' ? 1 : -1;
• Marc Adler: Can someone please help me with the formatting for my comment above? I tried indenting by 4 spaces, but I cannot get the text to show up as code.
• user10443653: thank you vert much. I will try to reprogram it based on your advice.