如何避免初始化已经初始化的变量？

Question

namespace text_test
{
public class txt_program


{
    public class txt
    {

        /* 0 */
        int[] M_array_0 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 1 */
        int[] M_array_1 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 2 */
        int[] M_array_2 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 3 */
        int[] M_array_3 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 4 */
        int[] M_array_4 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 5 */
        int[] M_array_5 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 6 */
        int[] M_array_6 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 7 */
        int[] M_array_7 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 8 */
        int[] M_array_8 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 9 */
        int[] M_array_9 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 10 */
        int[] M_array_10 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 11 */
        int[] M_array_11 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 12 */
        int[] M_array_12 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 13 */
        int[] M_array_13 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

        int[][] M = { M_array_0, M_array_1 };

    }
}

}

出现与以下部分相关的错误：

int[][] M = { M_array_0, M_array_1 };

错误涉及上面的M_array_0和M_array_1。我不明白的是为什么我不能从上面创建一个多维数组。我应该使用那个代码？我试过了：

string[][] M = { M_array_0, M_array_1 };
double[][] M = { M_array_0, M_array_1 };

错误显示：

A field initializer cannot reference the non-static field, method, or property 'txt_program.txt.M_array_0' text_test \psf\Home\Documents\Visual Studio 2015\Projects\text_test\text_test\text.cs 45 Active

提前谢谢。

Answer 1

A field initializer cannot reference the nonstatic field, method, or property 'field' Instance fields cannot be used to initialize other instance fields outside a method. If you are trying to initialize a variable outside a method, consider performing the initialization inside the class constructor

Reference

另请参阅 this 以获得描述性答案。

Answer 2

一种方法是编写一个静态方法returns你想要的数组，并用它来分配字段：

public class txt
{
    private int[][] M = createArray();

    private static int[][] createArray()
    {
        /* 0 */
        int[] M_array_0 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 1 */
        int[] M_array_1 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 2 */
        int[] M_array_2 = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
        /* 3 */

        // Etc

        return new [] { M_array_0, M_array_1, M_array_2 /* etc */ };
    }
}

或者你可以像这样内联编写它（但这不太灵活）：

public class txt
{
    private int[][] M = 
    {
        new[] {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, // M_array_0
        new[] {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, // M_array_1
        new[] {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, // M_array_3

        // Etc
    };
}

由于您将所有数组初始化为相同大小并包含零，因此您可以将其缩短为：

public class txt
{
    int[][] M = 
    {
        new int[14], // M_array_0
        new int[14], // M_array_1
        new int[14], // M_array_2

        // Etc
    };
}

但是，我怀疑这只是您给出的示例，在实际代码中您会使用非零值。

另请注意，您可以将 M 声明为只读：

private readonly int[][] M = ...

我建议您这样做，除非您需要在创建 class 实例后更改数组本身（而不是内容）。

Answer 3

我建议使用 Linq 以便生成数组

int[][] M = Enumerable.Range(0, 13) // 13 rows
  .Select(x => new int[13])         // each line contains 13 items
  .ToArray();

如何避免初始化已经初始化的变量？

How do I avoid initializing an already initialized variable?

c#

arrays

field