test.cs

[HttpPost]
public IActionResult FormValues(string Username) {

  // read stream to retrieve form field values
  Stream inputStream = Request.Body;
  FormField[] fields;

  StreamReader str = new StreamReader(inputStream);

  string sBuf = str.ReadToEndAsync().Result;
  fields = (FormField[])JsonConvert.DeserializeObject(sBuf, typeof(FormField[]));

  // write the values
  DeploymentHelpers.WriteValue(Username, fields);

  return Ok();
}