如何更改双数组中的项目？

Question

如何根据简单条件更改双变量中的项目？

检查这个例子：

public partial class Form1 : Form
{

    double[] vk = new double[11] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

    ...
    ...

    void setDouble()
    {
        if (bunifuDropdown1.selectedIndex == 0)
        {
            double[] vk = new double[11] { 2, 4.86, 11.81, 28.68, 69.64, 169.13, 410.75, 997.55, 2422.61, 5883.49, 21000 };
        }
        if (bunifuDropdown1.selectedIndex == 1)
        {
            double[] vk = new double[11] { 2, 4.51, 10.14, 22.81, 51.31, 115.46, 259.78, 584.51, 1315.14, 2959.07, 21000 };
        }
        if (bunifuDropdown1.selectedIndex == 2)
        {
            double[] vk = new double[11] { 2, 6.86, 18.67, 47.33, 116.94, 286.01, 696.59, 1693.71, 4115.30, 9996.29, 21000 };
        }
        if (bunifuDropdown1.selectedIndex == 3)
        {
            double[] vk = new double[11] { 2, 6.51, 16.64, 39.43, 90.72, 206.12, 465.78, 1049.99, 2364.49, 5322.09, 21000 };
        }
        if (bunifuDropdown1.selectedIndex == 4)
        {
            double[] vk = new double[11] { 2, 6.86, 18.67, 47.33, 108.94, 264.58, 642.55, 1560.47, 3789.71, 9203.58, 21000 };
        }
        if (bunifuDropdown1.selectedIndex == 5)
        {
            double[] vk = new double[11] { 2, 6.51, 16.64, 39.43, 82.72, 186.12, 418.78, 942.24, 2120.05, 4770.11, 21000 };
        }
    }

执行函数后setDouble()，这些值没有改变。没有发现错误。我怎样才能解决这个问题？

Answer 1

您正在vk函数中重新声明，这会影响原始函数。
尝试这个：

public partial class Form1 : Form
{
    double[] vk = new double[11] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

    ...
    ...

    void setDouble()
    {
        if (bunifuDropdown1.selectedIndex == 0)
        {
            // NOTE: Here instead of "double[] vk = ..." we have "vk = ..."
            vk = new double[11] { 2, 4.86, 11.81, 28.68, 69.64, 169.13, 410.75, 997.55, 2422.61, 5883.49, 21000 };
        }
        if (bunifuDropdown1.selectedIndex == 1)
        {
            vk = new double[11] { 2, 4.51, 10.14, 22.81, 51.31, 115.46, 259.78, 584.51, 1315.14, 2959.07, 21000 };
        }
        if (bunifuDropdown1.selectedIndex == 2)
        {
            vk = new double[11] { 2, 6.86, 18.67, 47.33, 116.94, 286.01, 696.59, 1693.71, 4115.30, 9996.29, 21000 };
        }
        if (bunifuDropdown1.selectedIndex == 3)
        {
            vk = new double[11] { 2, 6.51, 16.64, 39.43, 90.72, 206.12, 465.78, 1049.99, 2364.49, 5322.09, 21000 };
        }
        if (bunifuDropdown1.selectedIndex == 4)
        {
            vk = new double[11] { 2, 6.86, 18.67, 47.33, 108.94, 264.58, 642.55, 1560.47, 3789.71, 9203.58, 21000 };
        }
        if (bunifuDropdown1.selectedIndex == 5)
        {
            vk = new double[11] { 2, 6.51, 16.64, 39.43, 82.72, 186.12, 418.78, 942.24, 2120.05, 4770.11, 21000 };
        }
    }

Answer 2

在您当前的代码中，您声明了vk 局部变量，该变量将在离开其作用域时消失：

void setDouble()
{
    if (bunifuDropdown1.selectedIndex == 0)
    {
        // Local variable...
        double[] vk = 
    }   // which will disappear here (on leaving its scope)

    ... 
    if (bunifuDropdown1.selectedIndex == 2)
    {
        // Yet another local variable...
        double[] vk = 
    }   // which will disappear here (on leaving its scope)
    ...
} 

请注意，这个巨大的setDouble函数使得这种错误很容易产生，也很难发现。

让我们将数据本身和业务逻辑分开，我们将有一个易于阅读的代码

   public partial class Form1 : Form {
      private static readonly double[][] s_AllVks = new double[][] {
        new double[] { 2, 4.86, 11.81, 28.68,  69.64, 169.13, 410.75,  997.55, 2422.61, 5883.49, 21000 },
        new double[] { 2, 4.51, 10.14, 22.81,  51.31, 115.46, 259.78,  584.51, 1315.14, 2959.07, 21000 }, 
        new double[] { 2, 6.86, 18.67, 47.33, 116.94, 286.01, 696.59, 1693.71, 4115.30, 9996.29, 21000 }, 
        new double[] { 2, 6.86, 18.67, 47.33, 108.94, 264.58, 642.55, 1560.47, 3789.71, 9203.58, 21000 },
        new double[] { 2, 6.51, 16.64, 39.43,  82.72, 186.12, 418.78,  942.24, 2120.05, 4770.11, 21000 }, 
      }

      double[] vk = new double[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }; 

      void setDouble() {
        if (bunifuDropdown1.selectedIndex >= 0 && bunifuDropdown1.selectedIndex < s_AllVks.Length)
          vk = s_AllVks[bunifuDropdown1.selectedIndex] 
      }