I have the following logic that worked previously in umbraco 7.

The API Request

$http({
    method: 'POST',
    url: '/umbraco/backoffice/feed/feedapi/collectdata',
    headers: { 'Content-Type': undefined },
    transformRequest: function (data) {
        var formData = new FormData();
        formData.append("file", data.file);
        return formData;
    },
    data: {
        file: ctrl.settings.file
    }
});

The API

public async Task<IHttpActionResult> CollectData() {
    if (!Request.Content.IsMimeMultipartContent()) {
        return BadRequest("Unsupported media type.");
    }
    var id = Guid.NewGuid();
    var uploadFolder = SetupFolders(id);
    var provider = new NamedMultipartFormDataStreamProvider(uploadFolder);
    var result = await Request.Content.ReadAsMultipartAsync(provider);
    var file = result.FileData.First();
    var path = $"{uploadFolder}\\{file.Headers.ContentDisposition.FileName.Replace("\"", "")}";
    var jsonData = ParseJson(System.IO.File.ReadAllText(path));
    return Ok(new JObject {
        {"id", id },
        {"link", jsonData["link"] },
        { "items", jsonData["items"] }
    });
}

All this api is doing is uploading a file selected with a file input to the server for further processing. The problem is that result.FileData has no data, so it fails. Any ideas?

For reference, the submitted data looks like

------WebKitFormBoundaryJJZgcyycBGHiB2UX
Content-Disposition: form-data; name="file"

[object File]
------WebKitFormBoundaryJJZgcyycBGHiB2UX--

when I submit to the api.