I'm trying to figure out what information/metadata do files hold that could be a security risk? I have been looking around but couldn't find a simple answer, I'm worried that it may completely differ between file types.
In any case is there any general information that every file keeps (like creation date) that can be tracked or used against someone, and if there is, what method would be the easiest to clear this information from a file (using C#).
Or if I'm looking at the wrong place for help, could someone point me in the right direction please?
There can be different types of metadata for any file.
Whatever operating system and filesystem you use, the filesystem itself stores metadata about files. It can include things like where exactly the file is on the disk (which sectors), creation, modification time, owner, access rights, last access time, etc. It completely depends on the filesystem (and hence the OS). NTFS is different from good old FAT32, and these are very different from something like Ext4 on Linux.
Then any file can hold its own metadata as its contents. For example an image can hold Exif data, an mp3 can hold idv2 or idv3 tags (artist, song title, and so on), other filetypes can hold any other metadata in addition to the "actual" data. This completely depends on the filetype, the application developer that created the filetype (or the standard that describes it) made a decision what can be included.
If you are looking at this from a security perspective, almost any file can also hold "hidden" data, something called steganography. It's about hiding data in another piece of data, without the hidden part's presence being obvious. Say for example hiding a message (or a whole other file) in a valid image, without anybody only looking at the image knowing there is a hidden message.
So the difference here compared to filetype specific stuff is that in this case, there is no intended space for this data in the filetype, it's just encoded in smart ways into the file data itself, from where you can retrieve the info if you know how (and sometimes if you know some kind of a cryptographical secret).
Depending on storage hardware, I think your storage medium will also store some metadata internally. This may or may not concern you, and I'm not at all an expert in this unfortunately.