Using goto from if to while

Question

How can I stop using the goto here:

if(true)
{
    goto ln1;
}
DialogResult b=DialogResult.Yes;
while(b==DialogResult.Yes){
    //Stuff
    ln1: Function();  
}

Because using a goto from one scope to another is clearly not allowed.(It gives an error). So what can I do instead? I need to get to the SECOND line of code, not first.

Why are you using the `goto` here in the first place? It seems to be doing the same thing without it. — Benjamin Gruenbaum, Nov 23 '13 at 23:22
You should never, ever, ever, ever, ever (except in some niche situation) need to use goto in code. Certainly, your example should be refactorable to work without goto. goto can be a bit of a pain to debug - trust me, I've been there many times during my QuickBasic days. — Jason Evans, Nov 23 '13 at 23:28
This makes no sense since there is no link between `Function()` and `b`. — H H, Nov 23 '13 at 23:54
@Jason Evans "never, ever, ever, ever, ever" + exception is sligthly inconsequent, isn't it? — dhein, May 23 '14 at 07:10
@Zaibis OK, I'll reword. "You should rarely (except in some niche situation) need to use goto in code." — Jason Evans, May 23 '14 at 07:44

Guffa · Accepted Answer · 2013-11-23T23:56:27.953

3

If you want to enter the loop without an initial check of the condition, use a do ... while loop.

Example:

DialogResult b;
do {
   b = ShowDialog(myYesNoDialog);
} while(b == DialogResult.Yes);

If you want to use the initial check or not depending on a condition, use a boolean variable:

bool skipCondition = (some condition);
DialogResult b = DialogResult.Yes;
while (skipCondition || b == DialogResult.Yes) {
   skipCondition = false;
   b = ShowDialog(myYesNoDialog);
}

edited Nov 23 '13 at 23:56

answered Nov 23 '13 at 23:36

Guffa

687,336
108
737
1,005

1

@EdwardKarak: If you want to enter the loop without the initial check, then you don't need anything instead of `goto`, the `do ... while` loop does exactly that. If you want to use the initial check or not depending on a condition, I added an alternative for that above. – Guffa Nov 23 '13 at 23:58

score 1 · Answer 2 · edited May 23 '17 at 12:28

1

Do not use goto label; goto makes your code very complicated! I think you have to rethink in your classes design and your function workflow.
Very helpful link: 'Goto' is this bad?

var runFlag = false;
   if (true)
   {
       runFlag = true;
   }
   DialogResult b = DialogResult.Yes;
   while (b == DialogResult.Yes || runFlag) 
   {
     Function(); 
   }

edited May 23 '17 at 12:28

Community

1
1

answered Nov 23 '13 at 23:27

Bassam Alugili

16,345
7
52
70

1

Goto has nothing to break "OOP rules" - goto is a flow control construct. OOP is a coding paradigm. The two are really unrelated. The reason to avoid `goto` is because it's confusing to read code with `goto`. See http://www.cs.utexas.edu/users/EWD/ewd02xx/EWD215.PDF – Benjamin Gruenbaum Nov 23 '13 at 23:36
Well, sometimes it seems, `goto` is more readable than `break`. – JeffRSon Nov 23 '13 at 23:38
@User3805967 the paper I linked you to __IS__ Dijkstra's paper (maybe you should consider _reading_ it?). OOP talks about objects, their interactions and how program communication should happen. `goto` is a flow control construct, it's a part of the syntax, and has nothing to do with good or bad OOP. Claiming it does indicates lack of basic understanding of what a coding paradigm is, and what language syntax is (and how the two are connected in this case). Consider revising your answer to make sense. – Benjamin Gruenbaum Nov 23 '13 at 23:47
Maybe then my English description was really confusing. because we are agree with your last words. – Bassam Alugili Nov 23 '13 at 23:51
Ah great! Then please consider revising your answer and removing the irrelevant parts about "breaking OOP". – Benjamin Gruenbaum Nov 23 '13 at 23:51

score 0 · Answer 3 · answered Nov 23 '13 at 23:37

0

It seems to be something like that:

DialogResult b=...; // must be initialized - it's not correct to skip that

if(true)
{
    // goto ln1;
} else {
    b=DialogResult.Yes;
}
do
{
  /*ln1:*/ Function();
}
while(b==DialogResult.Yes);

answered Nov 23 '13 at 23:37

JeffRSon

10,404
4
26
51

score 0 · Answer 4 · answered Nov 23 '13 at 23:38

You do realise that your code skips a lot of lines so the program won't actually compile let lone run? What you have written is the same as

    do
{
    Function();
}while(b==DialogResult.Yes)

To make it work you'd need to execute

DialogResult b = DialogResult.Yes;

first

Using goto from if to while

4 Answers4