| Class | Description |
| BinaryReader | Reads primitive data types as binary values in a specific encoding. |
| BinaryWriter | Writes primitive types in binary to a stream and supports writing strings in a specific encoding. |
| BufferedStream | Adds a buffering layer to read and write operations on another stream. This class cannot be inherited. |
| Directory | Exposes static methods for creating, moving, and enumerating through directories and subdirectories. |
| DirectoryInfo | Exposes instance methods for creating, moving, and enumerating through directories and subdirectories. |
| DirectoryNotFoundException | The exception that is thrown when part of a file or directory cannot be found. |
| EndOfStreamException | The exception that is thrown when reading is attempted past the end of a stream. |
| ErrorEventArgs | Provides data for the Error event. |
| File | Provides static methods for the creation, copying, deletion, moving, and opening of files, and aids in the creation of FileStream objects. |
| FileInfo | Provides instance methods for the creation, copying, deletion, moving, and opening of files, and aids in the creation of FileStream objects. |
| FileLoadException | The exception that is thrown when a managed assembly is found but cannot be loaded. |
| FileNotFoundException | The exception that is thrown when an attempt to access a file that does not exist on disk fails. |
| FileStream | Exposes a Stream around a file, supporting both synchronous and asynchronous read and write operations. |
| FileSystemEventArgs | Provides data for the directory events: Changed, Created, Deleted. |
| FileSystemInfo | Provides the base class for both FileInfo and DirectoryInfo objects. |
| FileSystemWatcher | Listens to the file system change notifications and raises events when a directory, or file in a directory, changes. |
| InternalBufferOverflowException | The exception thrown when the internal buffer overflows. |
| IODescriptionAttribute | Sets the description visual designers can display when referencing an event, extender, or property. |
| IOException | The exception that is thrown when an I/O error occurs. |
| MemoryStream | Creates a stream whose backing store is memory. |
| Path | Performs operations on String instances that contain file or directory path information. These operations are performed in a cross-platform manner. |
| PathTooLongException | The exception that is thrown when a pathname or filename is longer than the system-defined maximum length . |
| RenamedEventArgs | Provides data for the Renamed event. |
| Stream | Provides a generic view of a sequence of bytes. |
| StreamReader | Implements a TextReader that reads characters from a byte stream in a particular encoding. |
| StreamWriter | Implements a TextWriter for writing characters to a stream in a particular encoding. |
| StringReader | Implements a TextReader that reads from a string. |
| StringWriter | Implements a TextWriter for writing information to a string. The information is stored in an underlying StringBuilder. |
| TextReader | Represents a reader that can read a sequential series of characters. |
| TextWriter | Represents a writer that can write a sequential series of characters. This class is abstract. |
