带/不带大括号的 C# Switch 语句....有什么区别?

C# Switch statement with/without curly brackets.... what#39;s the difference?(带/不带大括号的 C# Switch 语句....有什么区别?)

问题描述

Has C# always permitted you to omit curly brackets inside a switch() statement between the case: statements?

What is the effect of omitting them, as javascript programmers often do?

Example:

switch(x)
{
  case OneWay:
  {                               //  <---- Omit this entire line
    int y = 123;
    FindYou(ref y);
    break;
  }                               //  <---- Omit this entire line
  case TheOther:
  {                               //  <---- Omit this entire line
    double y = 456.7; // legal!
    GetchaGetcha(ref y);
    break;
  }                               //  <---- Omit this entire line
}

Curly braces are not required, but they might come in handy to introduce a new declaration space. This behavior hasn't changed since C# 1.0 as far as I know.

The effect of omitting them is that all variables declared somewhere inside the switch statement are visible from their point of declaration throughout all case branches.

See also Eric Lippert's example (case 3 in the post):

Four switch oddities

Eric's example:

switch(x)
{
  case OneWay:
    int y = 123;
    FindYou(ref y);
    break;
  case TheOther:
    double y = 456.7; // illegal!
    GetchaGetcha(ref y);
    break;
}

This does not compile because int y and double y are in the same declaration space introduced by the switch statement. You can fix the error by separating the declaration spaces using braces:

switch(x)
{
  case OneWay:
  {
    int y = 123;
    FindYou(ref y);
    break;
  }
  case TheOther:
  {
    double y = 456.7; // legal!
    GetchaGetcha(ref y);
    break;
  }
}

这篇关于带/不带大括号的 C# Switch 语句....有什么区别?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持编程学习网！