As mentioned in Solution, you need to upload have a file that needs to be uploaded. Archive that folder and then upload as a file. For this, you need to ask the users to archive the folders first — otherwise use an offline software to do that and upload the files to server.
First method will not work, browsers will not allow selection of folders. There is a
<input type="file" directory />
but that is not guaranteed to work. To know more on this, you need to understand how that input works,
How to get folder directory from HTML input type "file" or any other way? - Stack Overflow[
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HTML input type Attribute[
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Using files from web applications | MDN[
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Directory Chooser in HTML page - Stack Overflow[
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If you use second method then you can use the following class to zip a folder,
ZipFile
Class (System.IO.Compression)[
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