C# System.IO Namespace

The System.IO namespace provides classes and types for working with files, directories, and data streams in C#. It enables applications to create, read, write, copy, move, and manage files and folders efficiently.

In this chapter, you will learn what the System.IO namespace is, its commonly used classes, structures, delegates, enumerations, and practical examples of using the namespace.

What is the System.IO Namespace in C#?

The System.IO namespace is a built-in namespace in C# that contains classes, structures, delegates, and enumerations for performing input/output (I/O) operations. It provides functionality to work with files, directories, streams, memory, and path information.

Developers commonly use the System.IO namespace to create, read, write, copy, move, and delete files and directories.

Using the System.IO Namespace

To use the classes available in the System.IO namespace, include it at the beginning of your C# program.

Syntax

The following syntax is used to include the System.IO namespace in C#:

using System.IO;

In this syntax:

• using imports a namespace into the program.
• System.IO specifies the namespace that provides file and directory handling classes.

Common Classes in the System.IO Namespace

The System.IO namespace contains many classes for working with files, directories, streams, and memory.

Structures in the System.IO Namespace

The System.IO namespace provides structures that store information related to file system operations.

Delegates in the System.IO Namespace

The System.IO namespace contains delegates that are used with file system events.

Enumerations in the System.IO Namespace

The System.IO namespace provides several enumerations that define file access modes, sharing options, stream positions, and other file-related settings.

Examples of the System.IO Namespace

The following examples demonstrate how to use the System.IO namespace for common file operations.

Example 1: Creating and Writing to a Text File

This example shows how to create a text file and write data to it by using the File class from the System.IO namespace.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string path = "sample.txt";

        File.WriteAllText(path, "Welcome to C# System.IO Namespace.");

        Console.WriteLine("File created and data written successfully.");
    }
}

Output:

File created and data written successfully.

Explanation

In this example, we use the File.WriteAllText() method to create a text file and write a string to it. If the file already exists, its contents are replaced with the new text.

Example 2: Reading Data from a Text File

This example demonstrates how to read the contents of a text file by using the File.ReadAllText() method.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string path = "sample.txt";

        File.WriteAllText(path, "Welcome to C# System.IO Namespace.");

        Console.WriteLine("File created and data written successfully.");
    }
}

Output:

File Content:
Welcome to C# System.IO Namespace.

Explanation

In this example, we first check whether the file exists by using the File.Exists() method. If the file is available, the File.ReadAllText() method reads its entire contents and displays them on the console. This is one of the simplest ways to read text from a file in C#.