How to convert an int array to a nullable int array?

Question

Let's say I have an array containing x members and I want to create another array with the same Length (x) and the same integer values:

int[] arr = new int[x];
int?[] nullable_arr = arr;

And I can't do this:

int?[] arr = new int[x];

Is there an explicit conversion to a nullable type array or something I am not aware of?

Yes, I could simply convert each value in a loop but I'm asking if there is already an easy short way of doing this.

Any other "syntatic sugar" method will end up in looping through all items. You can use LINQ ro you can use `Array.ConvertAll` — Fabio, Jan 01 '17 at 21:20
@Fabio I think OP is indeed asking for a syntactic sugar. Why don't you post the `ConvertAll` method based answer which will be the best solution for arrays (not like the current answers which are more general, but also less efficient). — Ivan Stoev, Jan 01 '17 at 21:29

Fabio · Accepted Answer · 2017-01-01T21:45:26.820

8

Another aproach by using Array.ConvertAll method

var values = new[] {1, 2, 3, 4};
var nullableValues = Array.ConvertAll(ints, value => new int?(value));

Or with providing generic types explicitly

var nullableValues = Array.ConvertAll<int, int?>(ints, value => value);

edited Jan 01 '17 at 21:45

answered Jan 01 '17 at 21:41

Fabio

Of course OP has chosen the shortest to type, although it's the worse from the three posted (box + unbox). +1 – Ivan Stoev Jan 01 '17 at 21:44
I was just about to ask you how to do it with the Array.Convert All and yes i really forgot about boxing and unboxing thank you – SuperMinefudge Jan 01 '17 at 21:49
btw isnt doing this: "new int?(value)"boxing aswell? – SuperMinefudge Jan 01 '17 at 21:51
@SuperMinefudge No. Boxing is when you convert `int` to `object`. `Cast` is doing that because it operates on `IEnumerable` (note - not `IEnumerable`). So the equivalent of `Cast` is something like `arr.Select(x => (int?)(object)x)`. Btw, I'm glad you have changed your preference. – Ivan Stoev Jan 01 '17 at 21:55

score 7 · Answer 2 · answered Jan 01 '17 at 21:13

7

I suggest using Linq:

 int?[] nullable_arr = arr
   .Select(item => new int?(item))
   .ToArray();

answered Jan 01 '17 at 21:13

Dmitry Bychenko

score 5 · Answer 3 · answered Jan 01 '17 at 21:16

5

You could use Cast from Linq

int?[] arrNull = arr.Cast<int?>().ToArray();

answered Jan 01 '17 at 21:16

BrunoLM

3 Answers3