How can I copy files from streamingAssetsPath to persistentDataPath only when changed

Unity Engine
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1

I have some files(html and images) in streamAssetPath. Because in Android webview can’t read files in streamAssetPath, I copy them to persistentDataPath and read them.
For now I always copy the files when the webview is loaded, and I would like to change it only when the files in the streamAssetPath and the files in the PersistentDataPath are different from each other.
I can read information of files in the persistentDataPath using FileInfo class but I couldn’t find the way I can read information of files in streamAssetPath. Is there any way to do it?
Thank you in advance.

2

You could check checksums of the files, if you want to see if they are changed.
http://wiki.unity3d.com/index.php?title=MD5