Best way of accessing an object property that may be null?

Question

I want to know if there is a simple and clean way, like a method of sorts, of accesing an object property of a certain object even touhg this property could be null, that, in consecuence, this may throw a null pointer exception, and, if it is null, then do some other thing.

For example, I have my car object., that has two properties, Window, and Door., each one, Its an Object property.

Dim WCar = new Car with {.Door = new Door with {.Color = black}}

new Mgbox(WCar.Door.ToString & _
      WCar.Window.ToString) -> This may throw a null pointer exception.

(I do not own the class of the entity itself, and either know if this is safely coded in the constructor of the entity)

`new MsgBox(...)` what is that? `IsNot Nothing` will tell you if something is Nothing in older versions — Ňɏssa Pøngjǣrdenlarp, Feb 19 '18 at 16:22
How would you put it? Like this?: If (wcar.Window isnot nothing)... — Leandro Alberto Gamarra, Feb 19 '18 at 16:39
It would be faster to try it than ask on an internet web page. — LarsTech, Feb 19 '18 at 16:41
And what's the exception? Update your post if you have new information. — LarsTech, Feb 19 '18 at 16:44
Are you sure it's using the word "pointer"? If the Window property is null, you would get a NullReferenceException. — LarsTech, Feb 19 '18 at 16:49
Might be worthwhile to read [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/a/26761773/1070452) — Ňɏssa Pøngjǣrdenlarp, Feb 19 '18 at 16:56
Oh sorry, is NullReferenceException, Im basically trying to acces an object that does not exists. Anyways, Im going with the constructor solution., thank you! — Leandro Alberto Gamarra, Feb 19 '18 at 16:59
Actually, this is the real answer, It happens that Im using an older version of Visual Studio. Im clearly asking to avoid an exception, not what the exception is, in essence. https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/operators/null-conditional-operators — Leandro Alberto Gamarra, Feb 19 '18 at 17:10

score 2 · Accepted Answer · answered Feb 19 '18 at 16:21

2

You can use the null-conditional operator:

WCar.Window?.ToString()

If Window is Nothing this won't throw a NullReferenceException anymore, but ToString will return Nothing instead. If WCar could also be Nothing:

WCar?.Window?.ToString()

answered Feb 19 '18 at 16:21

Tim Schmelter

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Im currently working on Visual Studio 2008, It does not seem to work, it throws an error... touhg this is what I was exactly looking for. Thank you anyways! – Leandro Alberto Gamarra Feb 19 '18 at 16:38

score 1 · Answer 2 · answered Feb 19 '18 at 16:23

1

Maybe you can try to inherit the class and create your own setter and getter and validate if the property is null

answered Feb 19 '18 at 16:23

polzka90

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I was Actually going to inherit the class and asign an instance of an object, in the constructor, but the question came to mind so I asked... – Leandro Alberto Gamarra Feb 19 '18 at 16:41

Best way of accessing an object property that may be null?

2 Answers2