Nullable create via reflection with HasValue = false

Question

Given a type parameter which is a Nullable<>, how can I create an instance of that type which has HasValue = false?

In other words, complete this code:

public static Nullable<T> Create<T>() where T : struct 
{
    //Instantatie a Nullable<T> with reflection whose HasValue = false, and return it
}

Apologies, I made a mistake asking this question and have reposted: http://stackoverflow.com/questions/29627013/nullable-create-via-reflection-with-hasvalue-false-given-a-parameter-of-type — Ian Newson, Apr 14 '15 at 12:16
@Jamiec The two questions are different: one is `Create()`, while the other is `Create(Type type)`. While `return null` is a solution for both, the questions are surely different. — xanatos, Apr 14 '15 at 12:35
@xanatos - this question should probably be deleted by the OP (In actual fact I tried to get him to just update this question - see below). In any case this question is now defunct and should no longer attract answers. Finally, feel free to cast a re-open vote if you disagree, im not the dictator off all things right ;) — Jamiec, Apr 14 '15 at 13:12
@Jamiec I don't see why it couldn't still be helpful to someone else, which is why I didn't want to delete it. — Ian Newson, Apr 14 '15 at 13:16

xanatos · Answer 1 · 2015-04-14T12:10:17.640

3

return default(Nullable<T>)

is enough.

or even

return null;

or even

return new Nullable<T>();

Nullable value types have the paradox that new Nullable<T>() == null

edited Apr 14 '15 at 12:10

answered Apr 14 '15 at 12:07

xanatos

2

Can't you just `return null;`? – petelids Apr 14 '15 at 12:08
@petelids Nullable is structure - can't return null – NValchev Apr 14 '15 at 12:09
@NValchev Yes, it can :-) see https://ideone.com/WPKO5J – xanatos Apr 14 '15 at 12:10
1

@NValchev - see [this question](http://stackoverflow.com/questions/3775582/how-is-the-boxing-unboxing-behavior-of-nullablet-possible) for details. (+1 BTW xanatos!) – petelids Apr 14 '15 at 12:11

Jamiec · Accepted Answer · 2015-04-14T12:13:48.653

2

No reflection needed in this case.

public static Nullable<T> Create<T>() where T : struct 
{
    return new Nullable<T>(); // or default(Nullable<T>) 
}

edited Apr 14 '15 at 12:13

answered Apr 14 '15 at 12:08

Jamiec

I made a mistake in my question. While your post answers the question it doesn't solve my problem so will have to start a new question. – Ian Newson Apr 14 '15 at 12:10
@IanNewson - or you could just update this question. – Jamiec Apr 14 '15 at 12:12
I've created the other question, it doesn't seem fair to change the existing question since it's not your fault your perfectly valid answer doesn't solve my problem. – Ian Newson Apr 14 '15 at 12:15

2 Answers2