[FromForm] and lists are not serialized correctly?

Please see this stackoverflow post: https://stackoverflow.com/questions/55452461/a-list-of-guids-is-empty-when-passed-into-a-model-which-is-used-by-fromform-in

A short summary:

When using the default swagger configuration with a newly created ASP.NET Core 2.2 project and the following code, a [FromForm] model that contains a list will not be filled correctly.

A list of strings will contain 1 value that contains all values passed, but seperated by a comma.

I expect these things to be turned into a list containing x values?

Controller:

[HttpPost("bug")]
public ActionResult<string> Bug([FromForm] BugModel bugModel)
{
    var message = GetMessage(bugModel);

    return Ok(message);
}

Model:

public class BugModel
{
    /// <summary>
    /// If you send a GUID it will not appear in this list
    /// </summary>
    public IEnumerable<Guid> Ids { get; set; }
    
    
    /// <summary>
    /// If you send 3 strings, the list will contain 1 entry with the 3 string comma separated.
    /// </summary>
    public IEnumerable<string> IdsAsStringList { get; set; }
}

Swagger will, with some input values, generate the following CURL statement:

curl -X POST "https://localhost:5001/api/Bug/bug" -H "accept: text/plain" -H "Content-Type: multipart/form-data" -F "Ids="9dfb212a-a215-4991-9452-3ddf90e21ec0","9dfb212a-a215-4991-9452-3ddf90e21ec0"" -F "IdsAsStringList="9dfb212a-a215-4991-9452-3ddf90e21ec0","9dfb212a-a215-4991-9452-3ddf90e21ec0""

But this is wrong, at least for a default generated ASP.NET Core 2.2 project.

The following CURL statement, which has duplicate Ids fields, DOES work:

curl -X POST "https://localhost:5001/api/Bug/bug" -H "accept: text/plain" -H "Content-Type: multipart/form-data" -F "Ids="9dfb212a-a215-4991-9452-3ddf90e21ec0"" -F "Ids="9dfb212a-a215-4991-9452-3ddf90e21ec0"" -F "IdsAsStringList="9dfb212a-a215-4991-9452-3ddf90e21ec0","9dfb212a-a215-4991-9452-3ddf90e21ec0""

[bannarisoftwares]

Need fix for this bug

[PatrickGhosn]

We’ve just encountered this issue. We had to do a workaround like below, but of course this is not usable as every API generation will override this.

 if (ids) {
	// localVarFormParams.append('ids', ids.join(COLLECTION_FORMATS.csv));
	for (let index = 0; index < ids.length; index++) {
		localVarFormParams.append(`ids[${index}]`, ids[index].toString());
	}
}