Syntax for handling null values nicely

Question

When returning an object that may be null but mustn't I usually go with the (what its proper name?!) very-surprised operator: ?? like so.

return hazaa ?? new Hazaa();

The problem arises when I return a property of the object (in case it exists) and some default value otherwise. Not that the check of nullness is to be done on the parent object. Today I do like so.

return hazaa != null
  ? hazaa.Property
  : String.Empty;

I think it's a less than optimal syntax and I'd like it more compact (but still easily understandable, given that the property is implemented appropriately) like so.

return (hazaa ?? new Hazaa()).Property;

However, I dislike the parentheses and I'm looking for a syntax that omits them, still being compact. Is there such a thing in C#? I'm looking for something like this.

return hazaa ?.Property :String.Empty;

And, spinning on the thought, something like this.

return hazaa ?.Property :.BackUpProperty;

I could create my own property layer that gives me such behavior but that's just hiding the issue. :)

"null-coalescing operator", though I think I like the "very surprised operator" better. — Iridium, Aug 20 '13 at 10:36
No, basically there's nothing in C# like the null-safe dereferencing operator from Groovy. — Jon Skeet, Aug 20 '13 at 10:36
Wait, this would actually work ? `(hazaa ?? new Hazaa()).Property;` — Dimitar Dimitrov, Aug 20 '13 at 10:39
@DanielHilgarth No I just thought that If it's null in this situation it would just throw an error. Not sure why I'm under that impression. — Dimitar Dimitrov, Aug 20 '13 at 10:46
@Dimitar: `??` is the null-coalescing operator. It basically is short for `hazaa != null ? hazaa : new Hazaa()`. This should illustrate that there is no case where you actually would call `Property` on `null`. — Daniel Hilgarth, Aug 20 '13 at 10:48
@DanielHilgarth Yeah, it's kinda obvious now. I feel like an idiot ... — Dimitar Dimitrov, Aug 20 '13 at 10:50
@Dimitar: No need to. If you learned something new, everything is fine :) — Daniel Hilgarth, Aug 20 '13 at 10:52

score 3 · Answer 1 · answered Aug 20 '13 at 10:51

3

A Maybe monad might be a possible alternative.

Depending on the implementation it could look like this:

May.Be(hazaa, x => x.Property, string.Empty);

or

May.Be(hazaa).Select(x => x.Property, string.Empty);

answered Aug 20 '13 at 10:51

Daniel Hilgarth

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score 2 · Accepted Answer · edited Aug 20 '13 at 10:51

2

If you are interested in this topic, you should do some reading on monads. On the Maybe monad in particular. This should get you started: http://devtalk.net/csharp/chained-null-checks-and-the-maybe-monad/

There is no inbuilt syntax to simplify null checks in C#, sadly.

edited Aug 20 '13 at 10:51

Bridge

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answered Aug 20 '13 at 10:50

Nikita B

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There should be one. Maybe in C# 5.0. – Konrad Viltersten Aug 20 '13 at 15:33

Syntax for handling null values nicely

2 Answers2