Ran into this issue today and wanted to document it here in case I stumbled upon it again. I have a very simple API controller with a GET method to retrieve detailed information on some objects from the data store. The method accepts a collection of id values. Here is the API class and method signatures:

1
2
3
4
5
6
7

[Route("api/[controller]")]
[ApiController]
public class ItemController : Controller
{

  [HttpGet]
  public string GetDetails([FromQuery]int[] ids)

I was using Insomnia Rest to make a GET request to my controller using the following URL value:

1

localhost:5000/api/item/getdetails?ids=1&ids=2&ids=3

Sweet. Good to go. Click “Send” in Insomnia and watch my glorious integer array pass along my values and filter out my data.

Nope.

My integer array has a length of 0.

Wait. What? How?

No. That's not true. That's Impossible!

Turns out there is a bug. Apparently, the [ApiController] attribute breaks the [FromQuery] attribute for collection types in the version of dotnetcore I’m using.

Remove the [ApiController] attribute and all is well again.

Or

Specify the parameter name in the [FromQuery] attribute like [FromQuery(Name="ids")] and all is well again.

Oh, in case you are wondering. I’m currently running:

Dotnet Version 2.1.301 Commit 59524873d6