Thank you for sharing your findings with us and the community. When the debugger alters the behavior of the program.
RadAsyncUpload works in completely different manner and you won't receive the file in the controller directly. Normally, the file is uploaded to a handler and saved in a temporary folder until the page is submitted or the set timeout expires. You can skip this step and store the file directly in the handler as in the images uploader
demo. Then you can submit information about the uploaded file as part of the form (for example database record ID). With this information the controller action should be able to locate it and process it.
I hope this helps.
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