Hi Hem Upadhyaya,
There is no Reset Default value option for File Upload widget so it cannot be cleared directly.
As a workaround you can reload the mashup on UploadComplete event of File Upload widget.
You can use the Expression Widget to reload a Mashup fully by putting location.reload() in the expression parameter of the Widget.
I hope it helps.
Thanks Ankit Gupta for the workaround. Reloading mashup will work. However I don't want to reload entire mashup. The reason being that I have multiple widgets on the screen which may hold some values (like label, grid etc.) and they will get reset too.
Is there any other way out? Reloading the mashup is my last option.
You could also look into custom development and modifying the file upload widget (do make a copy of the original widget for backup purposes). Attached is some documentation on the custom extensibility.
I will also go ahead and place an enhancement request on your behalf; However, please keep in mind the delivery of enhancement requests is not guaranteed as it depends on current workload and availability of the R&D team, prioritizng bugs and existing issues.