C# switch/break | 易学教程

问题

It appears I need to use a break in each case block in my switch statement using C#.

I can see the reason for this in other languages where you can fall through to the next case statement.

Is it possible for case blocks to fall through to other case blocks?

Thanks very much, really appreciated!

回答1:

Yes, you can fall through to the next case block in two ways. You can use empty cases, which don't need a break, or you can use goto to jump to the next (or any) case:

switch (n) {
  case 1:
  case 2:
  case 3:
    Console.WriteLine("1, 2 or 3");
    goto case 4;
  case 4:
    Console.WriteLine(4);
    break;
}

回答2:

The enforcement of "break" is there to stop bugs. If you need to force a fall-thru then use "goto case " (replace the with appropriate value)

the following example shows what you can do:

switch(n)
{
    case 1:
    case 2:
      //do something for 1+2
      //...
      goto case 3;
    case 3:
      //do something for 3, and also extra for 1+2
      //...
      break;
    default:
      //do something for all other values
      //...
      break;
}

See http://msdn.microsoft.com/en-us/library/06tc147t%28VS.80%29.aspx

回答3:

C# doesn't support implicit fall through construct, but the break (or goto) nonetheless has to be there (msdn). The only thing you can do is stack cases in the following manner:

switch(something) {
    case 1:
    case 2:
      //do something
      break;
    case 3:
      //do something else
}

but that break (or another jump statement like goto) just needs to be there.

回答4:

In my C# (.NET 1.1, CF) code, both of these are allowed:

switch (_printerChoice) 
{
    case BeltPrintersEnum.ZebraQL220: 
        return new ZebraQL220Printer();
        break;
    case BeltPrintersEnum.ONeal: 
        return new ONealPrinter();
        break;
    default:            
        return new ZebraQL220Printer();         
                        break;  
}

switch (_printerChoice) 
{
    case BeltPrintersEnum.ZebraQL220: 
        return new ZebraQL220Printer();
    case BeltPrintersEnum.ONeal: 
        return new ONealPrinter();
    default:            
        return new ZebraQL220Printer();         
}

...but with the breaks in, they are grayed out, so considered moot. So, at least in my case, they are allowed but not required.

来源：https://stackoverflow.com/questions/1794696/c-sharp-switch-break

标签

switch-statement

break