Test. is null. specified an invalid value. is in an invalid format. An I/O error occurred while opening the file. specified a file that is read-only.-or- This operation is not supported on the current platform.-or- specified a directory.-or- The caller does not have the required permission. -or- is and the specified file is a hidden file. 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 characters. The specified path is invalid, (for example, it is on an unmapped drive).