How to make int array Nullable?

Question

I have this code:

var contractsID = contracts.Select(x => x.Id);
int?[] contractsIDList = contractsID.ToArray();//for debug

In this line:

int?[] contractsIDList = contractsID.ToArray();//for debug

I get this error:

Can not implicitly convert type int[] to int

what i try to do is to make contractsIDList Nullable type.

How to make int array Nullable?

[C# Nullable arrays](http://stackoverflow.com/questions/16069997/c-sharp-nullable-arrays) — huMpty duMpty, Oct 06 '15 at 13:34
Why do you want an array nullable? As a reference type it is already nullable. — K.J., Oct 06 '15 at 13:35
I don't understand the error message. Is `x.Id` an `int?` or an `int`? Do you actually want to create a `int?[]` from an `int[]`? — Tim Schmelter, Oct 06 '15 at 13:39
Your error message doesn't make sense for the code you are showing. — juharr, Oct 06 '15 at 13:48

stuartd · Accepted Answer · 2015-10-06T13:39:11.697

19

The error you should get is:

Can not implicitly convert type int[] to int?[]

Thus you need to convert the values:

int?[] contractsIDList = contractsId.Cast<int?>().ToArray();//for debug

edited Oct 06 '15 at 13:39

answered Oct 06 '15 at 13:37

stuartd

1

IMO, an ambiguous question has lead to a lot of disagreement. – spender Oct 06 '15 at 13:41

score 9 · Answer 2 · edited May 23 '17 at 11:54

But i guess that you actually want to get an int?[] from an int[](because the Id is not nullable). You can use Array.ConvertAll:

int[] contractsID = contracts.Select(x => x.Id).ToArray();
int?[] contractsIDList = Array.ConvertAll(contractsID, i => (int?)i);

or cast it directly in the LINQ query:

int?[] contractsIDList = contracts.Select(x => (int?) x.Id).ToArray();

score 5 · Answer 3 · answered Oct 06 '15 at 13:38

5

The easiest way in your case is to get int? from the Select:

var contractsID = contracts.Select(x => (int?)x.Id);
int?[] contractsIDList = contractsID.ToArray();

answered Oct 06 '15 at 13:38

Jakub Lortz

1

Could also be expressed as `contracts.Select(x => new int?(x.Id));` – stuartd Oct 06 '15 at 14:02

Ramankingdom · Answer 4 · 2015-10-07T08:42:21.610

1

Use this One

int?[] contractsIDList = contractsID.ConvertAll<int?>((i) => { int? ni = i; return ni; }).ToArray();

edited Oct 07 '15 at 08:42

answered Oct 06 '15 at 13:50

Ramankingdom

I wondered if your 100% comment was true, it doesn't work at all. If `contractsID` is an array(what is it) you need to pass the array as parameter, it's not an instance method. – Tim Schmelter Oct 06 '15 at 14:01
OP has showed his code: `var contractsID = contracts.Select(x => x.Id);`, it's an `IEnumerable`. – Tim Schmelter Oct 07 '15 at 07:15

4 Answers4