Why do IF statements sometimes use { } and others not?

July 17th, 2016, 04:42 PM

I'm trying to understand how IF statements work. In some examples from Ninjatrader, I will see if statements used without {then} brackets. But without them, I guess I don't understand how it would work.

Example:

if (condition_a)
variable = 123;

if(condition_b) {
variable = 555;
}

if(condition_c) {
variable= 444;

if(condition_c2)
variable=445;
}

I'm confused. Especially about nesting the IF's and when when/not to use the {} brackets.

July 17th, 2016, 08:45 PM

In C# when the condition of the if statement is true, the statement immediately after will be executed. If not true the statement immediately after is skipped.

In the case of if(condition) action; that is all that happens. So it can be written as shown or as you have seen as if (condition) {action}; Either one is correct and will work.

The "{}" are used to encapsulate the action as there can be more than one action statement, for example:
if (Condition)
{
action 1;
action 2;
action 3;
etc;
}

In the above example when the condition is true all of the action statements would be executed.

What is confusing is that you have seen it written so many ways but the main view is if the condition is true only one statement (or statements if encapsulated in {}) after will be executed.

Some people from a coding style perspective will use {} even if only one action statement is contained and they would do this to be consistent in their code style or perhaps readability as when you see { } you would know that all things between them are related by a condition statement.

Here is a link to the Ninjatrader7 helpguide educational section: NinjaTrader Version 7 which seems to advise if (condition {action;}

You might look at msdn for coding style guidlines: https://msdn.microsoft.com/en-us/library/ff926074.aspx

You might try a search on the internet for C# questions as you will find lots of reference materials.

Hope this has helped.

July 17th, 2016, 09:18 PM

Great explanation, thank you.

July 17th, 2016, 10:04 PM

@Jayswiss

Save yourself future debugging problems and just always use the brackets, even if its only one line of action.

July 18th, 2016, 09:08 AM

srgtroy

@Jayswiss

Save yourself future debugging problems and just always use the brackets, even if its only one line of action.

Correct.

Otherwise, you will find yourself doing this:

First version of a piece of code:

if (condition)
doThis; // This is completely valid, and executes doThis only if the condition is true. It skips it if condition is false.

(Or, you could put doThis on the same line -- "white space", including line breaks, don't matter.)

But then you want to add something that will also execute based on condition, but you are hasty and you write it like this:

if (condition)
doThis;
alsoDoAnotherThing;

// This will execute doThis if the condition is true, AND IT WILL ALWAYS EXECUTE alsoDoAnotherThing, whether condition is true or false, because it's the next statement after doThis.

But putting them in brackets will make both statements a block, as @Tasker_182 said, and the code will execute or skip the entire block, based on whether condition is true or not:

if (condition)
{
doThis;
alsoDoAnotherThing;
}

There is nothing wrong with not using the brackets if you have only one thing to execute, but you open yourself up to simple human errors that are hard to debug afterwards.

Bob.

Why do IF statements sometimes use { } and others not?

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Why do IF statements sometimes use { } and others not?