If statement with a null check

Question

I'm doing a null check for this object.

if (Myobject.EndofLife.Status == true) {
       //do some
}

When, 'EndofLife' property is null, we receive a 'Object reference' error.

So, modified to something like

if (Myobject.EndofLife != null && Myobject.EndofLife.Status == true)`

I can't seem to be using fancy operator here, like ?. or null coalescing operator (??).

Are there any fancy operators here (instead of my null check above)

I think there is a double question mark sign `??` that checks if something is null https://stackoverflow.com/questions/446835/what-do-two-question-marks-together-mean-in-c — Itsme1, Aug 24 '20 at 09:15
are you looking for ternary operator? `Myobject.EndofLife != null? //do something : // do somehting else` — Aarif, Aug 24 '20 at 09:15
@Itsme1 '??' is the null coalescing operator. That can't be used for the above scenario. — now he who must not be named., Aug 24 '20 at 09:17
@Aarif I don't want to create a new instance of 'EndofLife()'. I want to do a null check here. — now he who must not be named., Aug 24 '20 at 09:18

score 3 · Answer 1 · answered Aug 24 '20 at 09:19

3

Starting from C# 6 there is the Monadic null checking, so you can write:

if (Myobject.EndofLife?.Status == true) {

answered Aug 24 '20 at 09:19

gidanmx2

469
1
9
24

This wont work, This will give out 'Cannot implicitly convert bool? to bool – now he who must not be named. Aug 24 '20 at 09:23
What if MyObject is null? Then it throws a Nullreference Exception. – Matt Aug 24 '20 at 19:52
The question ask to control if EndofLife is a null property not also for Myobject.... but of course, the same syntaxt can be used for check every property/object – gidanmx2 Aug 25 '20 at 07:40

score 1 · Answer 2 · answered Aug 24 '20 at 09:21

1

Try this:

if (Myobject?.EndofLife?.Status ?? false) {
    //do some
}

answered Aug 24 '20 at 09:21

VirtualRiddles

11
2

OP said that he does not need a null coalescing operator – Itsme1 Aug 24 '20 at 09:22
@Itsme1 I didn't say i won't want it. I said it did not work for me in the first time. This answer cleverly uses both '?.' and '??' – now he who must not be named. Aug 24 '20 at 09:26

Matt · Accepted Answer · 2020-09-04T07:21:51.587

You can do:

    MyClass MyObject = null; // assuming the object wasn't instantiated
    if ((MyObject?.EndOfLife?.Status) ?? false == true)
    {
        // do something
    }

The expresseion

    ((MyObject?.EndOfLife?.Status) ?? false)

also covers the case when MyObject was instantiated, but EndOfLife wasn't, i.e.

     MyClass MyObject = new MyClass(); // EndOfLife is null

As you can see, it avoids Nullreference-Exceptions and it assumes false if any objects are null - so, if either MyObject is null or EndOfLife is null, then the code will not throw an exception.

Provided the classes you defined are like:

class MyClass
{
    public EndOfLifeInfo EndOfLife { get; set; }
}

public class EndOfLifeInfo
{
    public bool Status { get; set; }
}

Note: As @oerkelens mentioned correctly, == true is redundant and can be removed, but for understanding the code it is easier to read.

Yes I agree, `== true` is redundant - but it is easier to read. @oerkelens — Matt, Aug 24 '20 at 13:48

If statement with a null check

3 Answers3