Cannot send a collection of integers to a Web Core Api Post method, it is set to null

Question

I want to send a collection of integers to a post method on a web core api.

The method is;

[HttpPost("open")]
public IActionResult OpenInspections([FromBody]IEnumerable<int> inspectionIds)
{
    return NoContent();
//...

This is just for testing, I put a break point on the return statement and the inspectionIds payload is null.

In Postman I have

EDIT: I have just removed the square brackets from the signature. I was trying both IEnumerable<int> and int[] but neither worked

Answer 1

It is null because what is posted and what is expected by the action do not match, so it does not bind the model when posted. Example data being sent has a string array ["11111111", "11111112"] and not int array [11111111, 11111112],

also IEnumerable<int>[] represents a collection of collections, like

{ "inspectionIds": [[11111111, 11111112], [11111111, 11111112]]}

To get the desired behavior either update action to expect the desired data type

[HttpPost("open")]
public IActionResult OpenInspections([FromBody]int[] inspectionIds) {
    //...
}

Making sure that the posted body also matches what is expected

[11111111, 11111112]

OR

consider using a concrete model as the posted data in the provided question is a JSON object.

public class Inspection {
    public int[] inspectionIds { get; set; }
}

And update the action accordingly

[HttpPost("open")]
public IActionResult OpenInspections([FromBody]Inspection model) {
    int[] inspectionIds = model.inspectionIds;
   //...
}

the model would also have to match the expected data being posted.

{ "inspectionIds": [11111111, 11111112] }

Note that if the desired ids are suppose to be int then do not wrap them in quotes.