What is the real meaning of if(!bool)?

Question

I was wondering, what does exactly mean ! in the given expression :

bool myBool = AnyMethodThatReturnABoolean();
if(!myBool)
{
    // Do whatever you want
}

I now that I'm already using it when I expect myBool to be false, but is it more complex ?

Does ! mean "== false" or "!= true"?

What would be the difference between `== false` and `!= true`? — Corak, Jul 04 '19 at 08:56
Are you considering non-standard scenarios where a bool is returned that isn't internally 0 or 1 but some other number? — harold, Jul 04 '19 at 08:58
`if (myBool)` means `if (myBool == true)` and `if (!myBool)` means `if (myBool == false)`. — 41686d6564 stands w. Palestine, Jul 04 '19 at 09:00
Consider reading the documentation or searching on Google for **at least** 5 minutes before asking us to do the search for you — Camilo Terevinto, Jul 04 '19 at 09:01
first negate the value of myBool if the output of it is true, then execute the block — Ramesh, Jul 04 '19 at 09:03
@Corak and harold, it can be usefull to know for a case where you use a nullable boolean (bool?). — Zoma, Jul 04 '19 at 09:23
@MatthieuFoltzer - agreed, but your example explicitly uses `bool`, not `bool?`. — Corak, Jul 04 '19 at 09:40
@MatthieuFoltzer - no. With `bool?` it *does* make a difference to ask for `== false` or `!= true` (or `!value` for that matter) in the specific case of not having a value. `((bool?)null) == false` returns `false`. `((bool?)null) != true` returns `true` and `!((bool?)null)` returns `null`. — Corak, Jul 04 '19 at 10:00

AgentFire · Answer 1 · 2020-11-02T16:44:36.713

2

It simply inverts the value of the bool expression.

True becomes False and False becomes True.

if block will run only if expression inside the parentheses evaulates to True.

edited Nov 02 '20 at 16:44

answered Jul 04 '19 at 08:56

AgentFire

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score 2 · Accepted Answer · answered Jul 04 '19 at 08:57

It's the logical negation operator.

The ! operator computes logical negation of its operand. That is, it produces true, if the operand evaluates to false, and false, if the operand evaluates to true.

In your example

if(!myBool)

is like writing:

if(myBool == false)

score 1 · Answer 3 · answered Jul 04 '19 at 08:59

1

it's the same as:

if(mybool == false){ 

      //some code
}

Just a shorthand way of writing it.

answered Jul 04 '19 at 08:59

Nick

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What is the real meaning of if(!bool)?

3 Answers3