Retrieves the size of a file or alternate stream.
This method retrieves the size, in bytes, of the file or alternate stream specified by FileName. (Note that, for files, the returned value only reflects the size of the file's immediate contents, it does not account for any alternate streams the file may or may not contain.)
The value passed for FileName must be a vault-local absolute path.
Note: This method can only be called when Active is true.