How do I add null to a List of generic type? [duplicate]

Question

I am trying to do this:

protected List<T> list = new List<T>(); for (int i = 0; i < size; i++) { list.Add(null); }

I get a compiler error saying "cannot convert from null to T".

I have looked around but could not find an answer to this question.

@David I spent a while trying to figure this out, T is a reference type and once I added where T : class to the constraints I was able to add the null member. Avoidable question, but maybe someone else runs into this problem and can benefit from this. — AbandonedCrypt
– AbandonedCrypt, Commented Feb 15, 2021 at 18:46
list = Enumerable.Repeat(default(T), size).ToList(); note, that if T is struct (e.g. int, bool etc.), default(T) will not be null — Dmitrii Bychenko
– Dmitrii Bychenko, Commented Feb 15, 2021 at 19:00

AbandonedCrypt · Accepted Answer · 2021-02-15 18:44:31Z

0

Okay, I'm sorry, literally a few seconds after posting this I noticed I didnt put a constraint into the class header and when including where T : class in the constraints, I can null the list member.

answered Feb 15, 2021 at 18:44

AbandonedCrypt

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5 Comments

Dennis_E Over a year ago

Or you can use default(T)

AbandonedCrypt Over a year ago

@Dennis_E that's actually a great one

Guru Stron Over a year ago

@Dennis_E I would say you should post thus as an answer.

AbandonedCrypt Over a year ago

@Dmitry Bychenko (initial quesiton comments) correctly stated, that default(T) will not equate to null when dealing with structs like int, bool, etc

insane_developer Over a year ago

If the goal is to specifically add null to the list, default(T), in and of itself, does not guarantee so, therefore it wouldn't be a good answer to this post.

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