Good day to you.
We have checked your reported query that “cannot read code of null” error in all possible cases, the issue occurs only whenever the root path doesn’t contain any files or folders. We are suspect the same case also happened at your end. For your reference we have prepared and attached a video to exhibit the request sending to the server side.
Also, we have prepared a file manager sample in .NET Core. Refer the sample link below.
Can you please check with attached video and sample? If the issue persist, can you please share the below requested additional details will be more helpful to identify your reported issue at earlier.
a. Video for issue reproducing.
b. Code snippet for file manager operations in controller side.
c. Issue reproducing sample (if possible).