c# - 为什么我不能在范围内的 switch 语句中使用 "constant"？

Question

使用这段代码:

public partial class Form1 : Form
{
    private static readonly int TABCONTROL_BASICINFO = 0;
    private static readonly int TABCONTROL_CONFIDENTIALINFO = 1;
    private static readonly int TABCONTROL_ROLESANDSECURITY = 2;
    private static readonly int TABCONTROL_INACTIVEINFO = 3;
. . .
int ActiveTabPage = tabControlWorker.SelectedIndex;
switch (ActiveTabPage) {
    case TABCONTROL_BASICINFO:
        if (currentNode == "NodeBuckingham") {
        } else if (currentNode == "NodeNamath") {
        } else if (currentNode == "NodeParsons") {
        } else {
        }
    break;

...我必须用“0”替换“TABCONTROL_BASICINFO”，否则我会得到“一个常量值是预期”

Murgatroyd 的天堂!它不能查找并看到 TABCONTROL_BASICINFO 为 0 吗？

Answer 1

如果你想让它成为编译器所关心的常量表达式，将它声明为const:

// Note that static readonly is implied here
private const int TABCONTROL_BASICINFO = 0;

或遵循 .NET 命名约定...

private const int TabControlBasicInfo = 0;

或者使用枚举，假设你基本上有一组固定的值:

private enum TabControlType
{
    // Could ditch the explicit values here if you want
    BasicInfo = 0,
    ConfidentialInfo = 1,
    ...
}

顺便说一句，你也可以在 C# 中打开字符串，所以这样:

 if (currentNode == "NodeBuckingham") {
 } else if (currentNode == "NodeNamath") {
 } else if (currentNode == "NodeParsons") {
 } else {
 }

可以变成:

 switch (currentNode) {
     case "NodeBuckingham":
         ...
         break;
     case "NodeNamath":
         ...
         break;
     case "NodeParsons":
         ...
         break;
     default:
         ...
         break;
 }