break; issue in switch statement

[ddanbe]

I have no problem of putting a break statement in the default option of a switch case statement, just wondering why it is needed. Anyone any ideas?

int a = 42;
            switch (a)
            {
                case 1 : 
                case 2 : //statements for case 1 and 2
                    break;
                    // probably more case here
                default:
                    Console.WriteLine("We are here");
                    break;
            }

If I leave the break out on line 10, I get the error Control cannot fall through from one case label ('default:') to another but as it is the last statement in this situation, I'm a bit puzzled.

[IIM]

When a switch statement contains more than one switch section, you must explicitly terminate each section, including the last one, by using one of the following keywords:

return

goto

break

throw

continue

http://msdn.microsoft.com/en-us/library/vstudio/843c4c28.aspx

[ddanbe]

Thanks for your answer IIM, but my code compiles fine and works. It would execute statements if a is either 1 or 2. It will use the default if the variable a is 42 for example. But why the break in the default is needed? Fall through can be handy in some situations.

[gusano79]

I agree that fall-through can be handy, and I do occasionally lament its absence at my day job. But Microsoft seems to have been interested in lowering barriers to entry for a long time now, and AFAICT, this was just a decision the language designers made to prevent foot-shooting. My guess is that they required the last block to have a break as well just for consistency--they already assume we can't handle fall-through; why confuse us further? Eh, nichevo. =P

[IIM]

Execution of the statement list in the selected section begins with the first statement and proceeds through the statement list, typically until a jump statement is reached, such as a break, goto case, return, or throw. At that point, control is transferred outside the switch statement or to another case label.

Unlike C++, C# does not allow execution to continue from one switch section to the next. The following code causes an error.

The requirement in C# is that the end of every switch section, including the final one, is unreachable. Although this requirement usually is met by using a jump statement, the following case also is valid, because the end of the statement list cannot be reached.

C#

    case 4:
         while (true)
             Console.WriteLine("Endless looping. . . .");

Read these two paragraphs taken from http://msdn.microsoft.com/en-us/library/vstudio/06tc147t.aspx

[deceptikon]

But why the break in the default is needed?

default isn't special from a syntax standpoint, it's just another case. The reason a break is required is the same reason it's required in other cases, due to the fact that default isn't required to be the last case in the switch statement. A less common but equally valid positioning is the first case:

switch (a)
{
    default:
        Console.WriteLine("We are here");
        break;
    case 1:
    case 2:
        break;
}

And there's no requirement that default not be somewhere in the middle, though it's more confusing to read, of course. The designers of C# could have added an exception such that the last case in a switch statement doesn't require a break, but that would introduce more complexity to the language, the compiler, and force programmers to learn yet another nuance. I'd guess this was the reason it wasn't added.

[ddanbe]

Thanks all you people for the clarifications! As I said in my first post I have no problem with putting in a break or return or whatever. I was just wondering . . .