Dynamically change the content of input drop down list values upon uploading a file

I would like my dash app to populate the dropdown list dynamically using the column names of a file that I’d upload using the dcc.Upload component. Now the problem is that the dropdown is empty even after uploading the file. I tried refreshing the app but no luck. I closely adopted an example in the dash website where the content property of the dcc. Upload component is used to update the div’s children. I am not sure if the content of the UPLOAD component works only with the div component?. Please advise if anyone has stumbled into this issue.