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c#有没有简洁的方法跳出外层循环,类似Java那样使用标记的方式? 第1页

  

user avatar   rednaxelafx 网友的相关建议: 
       Let me google that for you

看搜索结果里头几个爆栈站的回答就够了。

简单来说C#没有Java能给循环打label的语法,所以没有直接对应的办法。

解决方案有三个流派:

  1. goto派:直接在外层循环后面放个label,在内层循环里需要跳出外层循环时用goto到那个label。要知道Java的labeled break本质上就是用于这个用途的受限版goto,用在这里再合适不过了。 <- 我是这个流派的。
  2. flag派:在外层循环前声明个bool flag,然后在内层循环结束后检查一下该flag有没有说要跳出循环:
    bool flag = false; for (...) {   for (...) {     if (...) {       flag = true;       break;     }   }   if (flag) break; }
    这大概是所谓“正统派”。
  3. 把内层循环封装成一个返回bool的方法,外层循环调用这个方法看返回值决定要不要break。

还有更变态的用抛/接异常来做的…滥用异常实现控制流派。这是异端,好孩子不要学,所以不列在“三个流派”中。不过我们也不能教条的批判它,也得看看它有趣的一面,例如:

Unchecked Exceptions Can Be Strictly More Powerful Than Call/CC
goto (C# Reference)

- MSDN

The goto statement transfers the program control directly to a labeled statement.

A common use of goto is to transfer control to a specific switch-case label or the default label in a switch statement.

The goto statement is also useful to get out of deeply nested loops.

C#规范说:

A label can be referenced from goto statements within the scope of the label. [Note: This means that goto statements can transfer control within blocks and out of blocks, but never into blocks. end note]

The target of a goto identifier statement is the labeled statement with the given label. If a label with the given name does not exist in the current function member, or if the goto statement is not within the scope of the label, a compile-time error occurs. [Note: This rule permits the use of a goto statement to transfer control out of a nested scope, but not into a nested scope. In the example
using System; class Test {   static void Main(string[] args) {     string[,] table = {       {"red", "blue", "green"},       {"Monday", "Wednesday", "Friday"}     };     foreach (string str in args) {       int row, colm;       for (row = 0; row <= 1; ++row)         for (colm = 0; colm <= 2; ++colm)           if (str == table[row,colm])             goto done;       Console.WriteLine("{0} not found", str);       continue;     done:       Console.WriteLine("Found {0} at [{1}][{2}]", str, row, colm);     }   } } 
a goto statement is used to transfer control out of a nested scope. end note]



  

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