Learn C# | File

File and Stream I/O

The System.IO namespace contains types that allow synchronous and asynchronous reading and writing on data streams and files.

The following distinctions help clarify the differences between a file and a stream. A file is an ordered and named collection of a particular sequence of bytes having persistent storage. Therefore, with files, one thinks in terms of directory paths, disk storage, and file and directory names. In contrast, streams provide a way to write and read bytes to and from a backing store that can be one of several storage mediums. Just as there are several backing stores other than disks, there are several kinds of streams other than file streams. For example, there are network, memory, and tape streams.

C# I/O Classes

The System.IO namespace has various class that are used for performing various operation with files, like creating and deleting files, reading from or writing to a file, closing a file etc.

The following table shows some commonly used non-abstract classes in the System.IO namespace:

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. This class cannot be inherited.
DirectoryInfo	Exposes instance methods for creating, moving, and enumerating through directories and subdirectories. This class cannot be inherited.
DirectoryNotFoundException	The exception that is thrown when part of a file or directory cannot be found.
DriveInfo	Provides access to information on a drive.
DriveNotFoundException	The exception that is thrown when trying to access a drive or share that is not available.
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.
FileFormatException	The exception that is thrown when an input file or a data stream that is supposed to conform to a certain file format specification is malformed.
FileInfo	Provides properties and instance methods for the creation, copying, deletion, moving, and opening of files, and aids in the creation of FileStream objects. This class cannot be inherited.
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	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.
InvalidDataException	The exception that is thrown when a data stream is in an invalid format.
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 path or file name is longer than the system-defined maximum length.
PipeException	Thrown when an error occurs within a named pipe.
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.
UnmanagedMemoryAccessor	Provides random access to unmanaged blocks of memory from managed code.
UnmanagedMemoryStream	Provides access to unmanaged blocks of memory from managed code.

The FileStream Class

The FileStream class in the System.IO namespace helps in reading from, writing to and closing files. This class derives from the abstract class Stream.

You need to create a FileStream object to create a new file or open an existing file. The syntax for creating a FileStream object is as follows:

FileStream <object_name> = new FileStream( <file_name>,
<FileMode Enumerator>, <FileAccess Enumerator>, <FileShare Enumerator>);

For example, for creating a FileStream object F for reading a file named sample.txt:

FileStream F = new FileStream("sample.txt", FileMode.Open, FileAccess.Read, FileShare.Read);

Parameter	Description
FileMode	The FileMode enumerator defines various methods for opening files. The members of the FileMode enumerator are: Append: It opens an existing file and puts cursor at the end of file, or creates the file, if the file does not exist. Create: It creates a new file. CreateNew: It specifies to the operating system, that it should create a new file. Open: It opens an existing file. OpenOrCreate: It specifies to the operating system that it should open a file if it exists, otherwise it should create a new file. Truncate: It opens an existing file and truncates its size to zero bytes.
FileAccess	FileAccess enumerators have members: Read, ReadWrite and Write.
FileShare	FileShare enumerators have the following members: Inheritable: It allows a file handle to pass inheritance to the child processes None: It declines sharing of the current file Read: It allows opening the file for reading ReadWrite: It allows opening the file for reading and writing Write: It allows opening the file for writing

Parameter

Description

FileMode

The FileMode enumerator defines various methods for opening files. The members of the FileMode enumerator are:

Append: It opens an existing file and puts cursor at the end of file, or creates the file, if the file does not exist.
Create: It creates a new file.
CreateNew: It specifies to the operating system, that it should create a new file.
Open: It opens an existing file.
OpenOrCreate: It specifies to the operating system that it should open a file if it exists, otherwise it should create a new file.
Truncate: It opens an existing file and truncates its size to zero bytes.

FileAccess

FileAccess enumerators have members: Read, ReadWrite and Write.

FileShare

FileShare enumerators have the following members:

Inheritable: It allows a file handle to pass inheritance to the child processes
None: It declines sharing of the current file
Read: It allows opening the file for reading
ReadWrite: It allows opening the file for reading and writing
Write: It allows opening the file for writing

The FileStream class is derived from Stream class. This class can be used for reading from and writing to files such as bytes, characters, strings, and other data-type values to a file. Other class I have used in this sample is StreamWriter. The StreamWriter class's Write and WriteLine members write to a file.

In this sample code, I have used FileStream class to create a text file and StreamWrite to write text to the text file.

namespace mcFileStream
{
using System;
using System.IO;
public class mcLogFile
{
public static void Main(String[] args)
{
// Create a text file C:\temp\mcb.txt
FileStream fs = new FileStream(@"c:\temp\mcb.txt" , FileMode.OpenOrCreate, FileAccess.Write);
StreamWriter m_streamWriter = new StreamWriter(fs);
// Write to the file using StreamWriter class
m_streamWriter.BaseStream.Seek(0, SeekOrigin.End);
m_streamWriter.Write(" File Write Operation Starts : ");
m_streamWriter.WriteLine("{0} {1}", DateTime.Now.ToLongTimeString(), DateTime.Now.ToLongDateString());
m_streamWriter.WriteLine(" First Line : Data is first line \n");
m_streamWriter.WriteLine(" This is next line in the text file. \n ");
m_streamWriter.Flush();
// Read from the file using StreamReader class
// StreamReader m_streamReader = new StreamReader(fs);
// string str = m_streamReader.ReadLine();
}
}
}

C#

Learn step by step

File and Stream I/O

C# I/O Classes

The FileStream Class

Upcoming courses

Recent added COURSES

Top 5 Tutorials

Learn Now...