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args.fileData.fileSource missing from UploadEventArgs as described in

example. This part of the API is required in order to create unique file names on client side when attaching photos directly from camera on iPhone (or any other similar paste operation).

Here's the tag helper:


Here's the JS where I log args from Uploading event to console:

function onUpload(args) {

Here's the resulting console output:

  "fileData": {
    "name": "doc4.txt",
    "rawFile": {},
    "size": 5,
    "status": "File uploaded successfully",
    "type": "txt",
    "validationMessages": {

      "minSize": "",

      "maxSize": ""


    "statusCode": "2"


  "customFormData": [


      "concernId": "1"



  "cancel": false,

  "currentRequest": {},

  "name": "uploading"


If possible, please provide me a work-around while fixing the bug. Unfortunately I can't deal with it on the server-side, because your control creates an arbitrary number of copies of all of the posted files, which can be seen in the Request.Form.Files IFormFileCollection (another bug in itself). So I already have to write logic to delete multiple instances of the same file name to address that, thus cannot differentiate between two different files with the same name.