What in C # (. NET) can I read the file a bit and write?

Is this a joke? By default, everything works with bytes. Want bits you please yourself to disassemble them. By the way, in the file system the minimum exchange unit is a cluster, i.e. several nat. sectors, and the physical sector of the storage medium is usually 512 bytes. And what am I leading to? And besides that even byte-reading is to some extent a fiction.

And there is also a BitStream library. It fits at first sight.