Hi,
We received your image. This occurs when the user is trying to submit the page while the uploading is running. Take this page as an example:
http://demo.essentialobjects.com/Demos/AJAX%20Uploader/File%20List/Demo.aspxThere is an AJAXUploader and a Submit button. The proper sequence is for the user to upload the file first, then click "Submit" to submit the uploaded file (to trigger FileUploaded event handler so that your code can decide what to do with the newly uploaded files). If however you click "Submit" button while the upload is in progress, then you will receive this error since FileUploaded event can't be triggered at that time as file uploading is still in progress.
The recommended way to handle this situation is to disable the submit button when your upload starts and then re-enabled it after it finishes (see the demo project for sample code). You can also handle ClientSideOnError as the message suggested. See here for details on how to handle client side event:
https://www.essentialobjects.com/doc/web/clientapi_howto.aspxAnd see here for the argument list of this event:
https://www.essentialobjects.com/doc/jsdoc.public.web.handlers.clientside_error_handler.aspxYou would need to write a JavaScript function with matching argument list, and set your uploader's ClientSideOnError to the
name of that function.
Hope this helps. Please feel free to let us know if you still have any more questions.
Thanks!