c# Force loop to check condition

Question

How do I force a loop to check its condition after every line of execution instead of only when the entire block finishes?

I have a while(!statement) { } loop, but statement can be changed by several different methods and should force the loop to break immediately after the current line in the loop has finished executing; instead of when the entire loop block has completed a cycle.

Is there any way to do this?

Answer 1

yes, but you won't like it... just put a if (!condition) break; after each instruction ;)

Answer 2

This is not how the language works. You will have to check at regular intervals:

while (processing)
{
    actionA();

    if (!processing)
        break;

    actionB();

    if (!processing)
        break;

    actionC();
}

Answer 3

I think that you would need an if statement after every line that could change the value, with a break if the condition was met.

Answer 4

Depending on what you are doing, you could consider having each statement be a delegate, create an array of delegates, and run a for loop across the array. That way the loop is just two lines: one that checks the condition, and when that executes the delegate at the current array position.

Answer 5

What about having those methods throw a custom exception and put a try-catch for the specific exception within your loop.

while (!condition) {
     try {
         //method calls
     } catch (CustomException ce) {
         break;
     }
    }

Answer 6

You could create a custom iterator (using the yield statement). The iterator would return each line (or multiple lines) you want to execute (using anonymous methods). You could then iterate through each line one at a time and check the condition inside the loop. Here is how it would look:

public delegate void DelegateType();

public static IEnumerable< DelegateType > GetStatements()
{
    // ---- replace with your code below ----
    yield return delegate() { Console.WriteLine("statement 1"); };
    yield return delegate() { Console.WriteLine("statement 2"); };
    yield return delegate() { Console.WriteLine("statement 3"); };
    yield return delegate() 
    { 
        // You can return multiples statements in one block.
        Console.WriteLine("statement 4"); 
        Console.WriteLine("statement 5");
    };
}

Here is how you would iterate through your statements and check the condition after each statement.

IEnumerable<DelegateType> statementList = GetStatements();
foreach (DelegateType statement in statementList)
{
    statement();                   // Here is where your statement executes.
    if (!ConditionContinue())      // Check your condition here.
    {
        break;
    }
}

Enjoy,

Robert C. Cartaino