无法让Dropzone.js发送其他数据

<form action="/api/photos/"
          class="dropzone needsclick dz-clickable"
          id="image-upload"
          method="post">
        <input type="hidden" name="eventId" value="1"/>
        <div class="dz-message needsclick">
            <span class="note needsclick">
                Drop files here or click to upload.
            </span>
        </div>
    </form>

<script>
            Dropzone.options.imageUpload = {
                dictDefaultMessage: "Drop files here or Click to Upload",
                addRemoveLinks: true, // Allows for cancellation of file upload and remove thumbnail
                init: function () {
                myDropzone = this;
                    myDropzone.on("sending", function (file, xhr, data) {
                data.append("message", "hello world");
                        console.log(data);
                    });
                    myDropzone.on("success", function (file, response) {
                console.log("Success");
                        myDropzone.removeFile(file);
                    });
                }
            };
    </script>

public async Task<IActionResult> PostPhoto(List<IFormFile> file)
        {
            ..code removed..
        }