C# - foreach loop within while loop - break out of foreach and continue on the while loop right away?

Question

while (foo() == true)
{
   foreach (var x in xs)
   {
       if (bar(x) == true)
       {
           //"break;" out of this foreach
           //AND "continue;" on the while loop.
       }
   }

   //If I didn't continue, do other stuff.
}

I'm a bit stuck on how to do this.

Update: I fixed the question. I left out the fact that I need to process other stuff if I don't call a continue; on the while loop.

Sorry, I didn't realize I used the word "something" twice.

just break; the while will continue because something is true — Djole
– Djole, Commented Jul 15, 2011 at 16:06
Sorry, I left something out. I need to be able to process additional items if I don't continue;. — myermian
– myermian, Commented Jul 15, 2011 at 16:08
then you need to either write if(something)continue; when you exit the foreach loop, or use goto label — Djole
– Djole, Commented Jul 15, 2011 at 16:11
Then edit the question so that it is clear! This question is very unclear. You are using "something" to mean two different things, it is very unclear where the necessary side effects are in these loops, and so on. It might be possible to rewrite this whole thing with no loops at all, or to refactor it into methods, or whatever, but without knowing what the actual problem is, it is difficult to say. — Eric Lippert
– Eric Lippert, Commented Jul 15, 2011 at 16:17

Eric Lippert · Accepted Answer · 2011-07-15 16:40:27Z

14

I would rewrite this:

while (foo() == true)
{
   foreach (var x in xs)
   {
       if (bar(x) == true)
       {
           //"break;" out of this foreach
           //AND "continue;" on the while loop.
       }
   }

   //If I didn't continue, do other stuff.
   DoStuff();
}

as

while (foo()) // eliminate redundant comparison to "true".
{
   // Eliminate unnecessary loop; the loop is just 
   // for checking to see if any member of xs matches predicate bar, so
   // just see if any member of xs matches predicate bar!
   if (!xs.Any(bar))        
   {
       DoStuff();
   }
}

answered Jul 15, 2011 at 16:40

Eric Lippert

663k185 gold badges1.3k silver badges2.1k bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

myermian Over a year ago

This is nicer than what I was trying to do. :)

Eric Lippert Over a year ago

@myermian: A good rule of thumb that I try to use: if a loop is for executing a particular side effect over and over again, then use a loop. If a loop is solely for computing a value, then move the loop into a helper function, or find a helper function that already does what you want -- like "Any", or "All", or "Sum", or whatever. That way you make the loop an implementation detail of the helper, rather than a nested control flow of your method.

myermian Over a year ago

Yea, I didn't even think about the Any or All functions. But, it ended up helping a lot. I flipped the if so it continues if it matches any and does the DoStuff() otherwise (Resharper agreed that inversing the if helps avoid nesting). This is way cleaner than having a bool value, setting it, breaking out of the for loop, checking the bool to see what the result was...

Ani Over a year ago

@myermian / eric: Out of curiosity, in what way is this different from my answer?

adrianos · Accepted Answer · 2011-07-15 16:04:21Z

6

while (something)
{
   foreach (var x in xs)
   {
       if (something is true)
       {
           //Break out of this foreach
           //AND "continue;" on the while loop.
           break;
       }
   }
}

answered Jul 15, 2011 at 16:04

adrianos

1,5812 gold badges18 silver badges24 bronze badges

5 Comments

myermian Over a year ago

Sorry, I left something out. I need to be able to process additional items if I don't continue;.

FiveTools Over a year ago

Smells like refactoring needed - I think you need to look at the conditional logic you're using...

adrianos Over a year ago

sorry, i didn't understand your comment or update - do you want to stay in the while after hitting the break?

myermian Over a year ago

Yea, I messed up by using the term "something" twice.

adrianos Over a year ago

but hitting the break in the for loop will continue the while loop

Ani · Accepted Answer · 2011-07-15 16:18:07Z

4

If I understand you correctly, you can use the LINQ Any / All predicate here:

while (something)
{
    // You can also write this with the Enumerable.All method
   if(!xs.Any(x => somePredicate(x))
   {
      // Place code meant for the "If I didn't continue, do other stuff."
      // block here.
   }
}

answered Jul 15, 2011 at 16:18

Ani

114k27 gold badges269 silver badges313 bronze badges

Comments

Adam Houldsworth · Accepted Answer · 2011-07-15 16:12:10Z

2

This should address your requirement:

while (something)
{   
    bool doContinue = false;

    foreach (var x in xs)   
    {       
        if (something is true)       
        {           
            //Break out of this foreach           
            //AND "continue;" on the while loop.          
            doContinue = true; 
            break;       
        }   
    }

    if (doContinue)
        continue;

    // Additional items.
}

This sort of code happens frequently as soon as you need break to propagate through nested constructs. Whether it is a code smell or not is up for debate :-)

answered Jul 15, 2011 at 16:12

Adam Houldsworth

64.8k11 gold badges161 silver badges190 bronze badges

Comments

FiveTools · Accepted Answer · 2011-07-15 16:11:17Z

0

while (something)
{
   foreach (var x in xs)
   {
       if (something is true)
       {
           break;
       }
   }
}

however, wouldn't both of these values always equate to true???

answered Jul 15, 2011 at 16:11

FiveTools

6,04816 gold badges65 silver badges84 bronze badges

Comments

Lourens · Accepted Answer · 2011-07-15 16:12:37Z

0

So you want to continue after breaking?

while (something)
{
    bool hit = false;

    foreach (var x in xs)
    {
        if (something is true)
        {
            hit = true;
            break;
        }
    }

    if(hit)
        continue;
}

answered Jul 15, 2011 at 16:12

Lourens

1,5181 gold badge13 silver badges27 bronze badges

Collectives™ on Stack Overflow

C# - foreach loop within while loop - break out of foreach and continue on the while loop right away?

6 Answers 6

4 Comments

5 Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

4 Comments

5 Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related