FileStream Constructor (String, FileMode) Assembly: mscorlib (in
mscorlib.dll) path is an empty string (""), contains only white
space, or contains one or more invalid characters. path refers
to a non-file device, such as "con:", "com1:", "lpt1:", etc. in
an NTFS environment. path refers to a non-file device, such as
"con:", "com1:", "lpt1:", etc. in a non-NTFS environment. path
is null. The caller does not have the required permission. The
file cannot be found, such as when mode is FileMode.Truncate or
FileMode.Open, and the file specified by path does not exist.
The file must already exist in these modes. An I/O error occurs,
such as specifying FileMode.CreateNew and the file specified by
path already exists. The stream has been closed. The specified
path is invalid, such as being on an unmapped drive. The
specified path, file name, or both exceed the system-defined
maximum length. For example, on Windows-based platforms, paths
must be less than 248 characters, and file names must be less
than 260 character