The key value to ValueProviderResult GetValue(string key) is "[0]"

[iMetro]

Tried using this on an [ApiController] Controller method:

[HttpGet]
public IEnumerable<int> Get([FromQuery]IEnumerable<int> id)
{
    return val;
}

When debugging in to GetValue in SeparatedQueryStringValueProvider.cs the key is not "id" as I would expect, instead its "[0]", so the comma separated values entered in the request (query string e.g values?id=100,200,300) will not be found and sent a long to my Get method in ValuesController.

I added a little hack to parse the key value "[0]", converting it to integer (index) and getting the key value ("id") from
_values.Keys.ElementAt(index.Value) which would now get the array values which are split up and returned with
return new ValueProviderResult(splitValues, result.Culture);
Although I send in more than one integer in the query string e.g values?id=100,200,300 only the first value in the integer array remains in the id parameter.

Its tested in a web api core 2.1 project.

Seems like the functionality of the the names of the key parameter coming to GetValue is changed? Based on position instead of name?
Any ideas?