Basics of File Handling in C#

File handling in C# allows developers to create, read, write and manage files stored on disk. The .NET Framework provides the System.IO namespace, which contains classes and methods for performing these operations in a simple and efficient way.

Namespaces and Classes for File Handling

C# uses the System.IO namespace for file and directory operations. Commonly used classes include:

• File: Provides static methods for creating, copying, deleting, moving and opening files.
• FileInfo: Provides instance methods for file operations with additional objec t-oriented features.
• Directory: Provides static methods for creating, moving and enumerating directories.
• DirectoryInfo: Provides instance methods for directory operations.
• StreamReader / StreamWriter: For reading and writing text files.
• BinaryReader / BinaryWriter: For reading and writing binary files.
• FileStream: For reading and writing to files at a lower level.

Creating a File

You can create a file using the File class or the FileStream class.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string path = "sample.txt";
        File.WriteAllText(path, "Hello, File Handling in C#!");
        Console.WriteLine("File created successfully.");
    }
}

Explanation

• File.WriteAllText creates the file if it doesn’t exist and writes the given string to it.
• If the file already exists, its contents are overwritten.

Writing to a File

You can write text data using StreamWriter.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        using (StreamWriter writer = new StreamWriter("data.txt"))
        {
            writer.WriteLine("Line 1");
            writer.WriteLine("Line 2");
        }
        Console.WriteLine("Data written to file.");
    }
}

Data written to file.

Explanation

• StreamWriter is wrapped in a using block to ensure the file is closed automatically.
• WriteLine writes each string to a new line in the file.

Reading from a File

You can read text files using StreamReader.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        using (StreamReader reader = new StreamReader("data.txt"))
        {
            string content = reader.ReadToEnd();
            Console.WriteLine("File Content:");
            Console.WriteLine(content);
        }
    }
}

Explanation

• ReadToEnd reads the entire file content into a single string.
• Alternatively, you can use ReadLine to read line by line.

Appending to a File

Appending adds data without deleting existing content.

File.AppendAllText("data.txt", "\nAppended Line");
Console.WriteLine("Line appended.");

Working with Binary Files

For binary data, use BinaryWriter and BinaryReader.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        using (BinaryWriter writer = new BinaryWriter(File.Open("numbers.bin", FileMode.Create)))
        {
            writer.Write(100);
            writer.Write(200);
        }

        using (BinaryReader reader = new BinaryReader(File.Open("numbers.bin", FileMode.Open)))
        {
            Console.WriteLine(reader.ReadInt32());
            Console.WriteLine(reader.ReadInt32());
        }
    }
}

Explanation

• BinaryWriter writes integers in binary format.
• BinaryReader reads them back in the same order.

File Information

The FileInfo class provides detailed information about files.

FileInfo fileInfo = new FileInfo("data.txt");
Console.WriteLine($"File Name: {fileInfo.Name}");
Console.WriteLine($"Size: {fileInfo.Length} bytes");
Console.WriteLine($"Created: {fileInfo.CreationTime}");

Directory Operations

The Directory and DirectoryInfo classes are used for folder management.

Directory.CreateDirectory("MyFolder");
Console.WriteLine("Directory created.");

string[] files = Directory.GetFiles(".");
Console.WriteLine("Files in current directory:");
foreach (string file in files)
    Console.WriteLine(file);

Key Points

1. Use System.IO namespace for file and directory operations.
2. File and FileInfo provide file operations, while Directory and DirectoryInfo manage folders.
3. Use StreamWriter and StreamReader for text files.
4. Use BinaryWriter and BinaryReader for binary files.
5. Always close or dispose streams to release resources.
6. Wrap file operations in try-catch to handle exceptions like FileNotFoundException or UnauthorizedAccessException.