对象 C# 的二维数组

Question

我知道，这个问题似乎被问了很多，但我仍然无法使用人们提供的解决方案来解决它。因此，在尝试使用二维对象数组时，我也遇到了异常“System.NullReferenceException：'对象引用未设置为对象的实例。'”。所以这是不工作的代码：

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Threading.Tasks;

    namespace Console_multi_fonctionnelle_basique
    {
        partial class Program
        {
             public class SudokuSolver
             {
                 //Initialisation code
                 public SudokuSolver()
                 {
                     GridValue[,] SudokuGrid = new GridValue[9, 9];
                     SudokuDisplay(SudokuGrid);
                     Console.ReadKey();
                }
                //Store values for every slot
                class GridValue
                {
                    public bool CanBe1 { get; set; } = false;
                    public bool CanBe2 { get; set; } = false;
                    public bool CanBe3 { get; set; } = false;
                    public bool CanBe4 { get; set; } = false;
                    public bool CanBe5 { get; set; } = false;
                    public bool CanBe6 { get; set; } = false;
                    public bool CanBe7 { get; set; } = false;
                    public bool CanBe8 { get; set; } = false;
                    public bool CanBe9 { get; set; } = false;
                    public bool AlreadySolved { get; set; } = false;
                    public int Value { get; set; } = 0;
                }
                //Display the grid
                void SudokuDisplay(GridValue[,] Sudoku)
                {
                    Sudoku[1, 1].Value = 1;
                    Sudoku[1, 2].Value = 2;
                    Console.WriteLine(Sudoku[0, 0].Value + Sudoku[1,0].Value);
                }
                //To Do
                //Ask the values for every slot
                //Verify if the slot can contain a number
                //Choose the most appropriated number for the slot
                //End the program after user pressing an key
            }
        }
    }

所以，如您所见，我想使用大小为 9x9 的“GridValue”类的 2D 数组，以便每个“Grid slot”都有自己的变量，以便以后解决数独问题。但是程序看起来不理解我的数组包含“GridValue”对象所以他似乎不理解每个数组值都包含多个变量......所以我想要的结果是我可以为其中一个对象定义变量数组没有异常。

Answer 1

我希望这个例子可以帮助你理解 OOP。欢迎加入社区！

using System;

namespace ConsoleApp1
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");

            SudokuSolver sudokuSolver = new SudokuSolver(9, 9);

            sudokuSolver.DisplayGrid();

            Console.ReadKey();
        }
    } 


    public class SudokuSolver
    {
        //Store every values needed for every "slot"
        public class GridValue
        {
            public bool CanBe1 { get; set; } = false;
            public bool CanBe2 { get; set; } = false;
            public bool CanBe3 { get; set; } = false;
            public bool CanBe4 { get; set; } = false;
            public bool CanBe5 { get; set; } = false;
            public bool CanBe6 { get; set; } = false;
            public bool CanBe7 { get; set; } = false;
            public bool CanBe8 { get; set; } = false;
            public bool CanBe9 { get; set; } = false;
            public bool AlreadySolved { get; set; } = false;
            public int Value { get; set; } = 0;
        }

        public GridValue[,] SudokuGrid { get; }

        //Code d'initialisation
        public SudokuSolver(int x, int y)
        { 
            // only initialize in the constructor, no calls
            SudokuGrid = new GridValue[x, y]; // the array exists now in mem, but each entry is pointing to null
            for (int i = 0; i < x; i++)
            {
                for (int j = 0; j < y; j++)
                {
                    SudokuGrid[i, j] = new GridValue();
                }
            }
        }



        //Display the grid => then name it that way!
        public void DisplayGrid()
        {
            SudokuGrid[1, 1].Value = 1;
            SudokuGrid[1, 2].Value = 2;
            Console.WriteLine(SudokuGrid[0, 0].Value + SudokuGrid[1, 0].Value);
        }


     }

}

Answer 2

您已经创建了一个空数组，因此当您尝试访问一个元素时，会引发异常。 初始化数组的元素，你应该没问题。

public class SudokuSolver
{
    //Initialisation code
    public SudokuSolver()
    {
        GridValue[,] SudokuGrid = new GridValue[9, 9];

    //###################

        for (int r=0; r < 9; r++) 
        { 
            for (int c = 0; c < 9; c++) 
            { 
                SudokuGrid[r, c] = new GridValue(); 
            } 
        }

    //###################

        SudokuDisplay(SudokuGrid);
        Console.ReadKey();
    }
    //Store values for every slot
    class GridValue
    {
        public bool CanBe1 { get; set; } = false;
        public bool CanBe2 { get; set; } = false;
        public bool CanBe3 { get; set; } = false;
        public bool CanBe4 { get; set; } = false;
        public bool CanBe5 { get; set; } = false;
        public bool CanBe6 { get; set; } = false;
        public bool CanBe7 { get; set; } = false;
        public bool CanBe8 { get; set; } = false;
        public bool CanBe9 { get; set; } = false;
        public bool AlreadySolved { get; set; } = false;
        public int Value { get; set; } = 0;
    }
    //Display the grid
    void SudokuDisplay(GridValue[,] Sudoku)
    {
        Sudoku[1, 1].Value = 1;
        Sudoku[1, 2].Value = 2;
        Console.WriteLine(Sudoku[0, 0].Value + Sudoku[1, 0].Value);
    }
    //To Do
    //Ask the values for every slot
    //Verify if the slot can contain a number
    //Choose the most appropriated number for the slot
    //End the program after user pressing an key
}