Question

Consider the following C#:

// C# .net
switch(x)
   {
    case 1:
        for(int i = 0; i < 10; i++)
        {
            int val = getValue(i);
            if (val == 0)
                goto endswitch;
        }
        doMoreStuff();
        break;
    case 2:
        doSomeThingElse();
        break;
    default: throw new ArgumentOutOfRangeException();
}
endswitch: ;

I’ve written code similar to the above code sample. The problem is that I need to break the switch statement from inside the inner for loop. If I put a break statement there, it will only break the inner for loop and then proceed to doMoreStuff(), which is not what I need.

The alternative that seems to work best here is a goto statement, but I know this is frowned upon.

Another alternative is to keep track of a separate variable inside the for loop, but this adds lines of code and is less elegent.

What is the best way to do this?

Update: I have read that there is a way to do this in JavaScript. It works like this: (http://www.devguru.com/technologies/ecmascript/quickref/break.html)

// JavaScript
outer_loop:
for(i=0; i<3; i++)
{
   document.write("<BR>" + "outer " + i + ":   ");
   for(j=0; j<5; j++)
   {
      document.write("inner " + j + " ");
      if(j==x)
         break outer_loop;
   }
}

Is something like this possible in C#?

Answer 1

You can abstract the check to a method with a return flag:

switch(x)
{
    case 1:
        if (ShouldDoMoreStuff())
            doMoreStuff();
        break;
    case 2:
        doSomeThingElse();
        break;
    default: throw new ArgumentOutOfRangeException();
}


private bool ShouldDoMoreStuff()
{
    for(int i = 0; i < 10; i++)
    {
        var val = getValue(i);
        if (val == 0)
            return false;
    }

    return true;
}

Just to expand, you can use the goto as you had, but it’s generally frowned upon, especially in such a trivial case. Sometimes it’s useful when you have many, many nested loops or switches but that’s usually a sign that maybe you should refactor/redesign a bit. As you pointed out, you can store a local variable and do a check but that’s a bit obtuse/smelly as you realized. I prefer this method I posted above as it becomes pretty readable to work with.

EDIT: Regarding your comment and edited question, I do not believe a analogous language feature to your JavaScript code exists in C#. From http://msdn.microsoft.com/en-us/library/37zc9d2w%28VS.80%29.aspx (emphasis added):

Within nested statements, the break statement terminates only the do,
for, switch, or while statement that immediately encloses it. You can
use a return or goto statement to transfer control from within more
deeply nested structures.