Introduction to File I/O in C

1. Introduction

In this tutorial, we will cover the basics of File Input/Output (I/O) in C#. File I/O is a critical part of most applications, allowing you to read from and write to files on your computer's hard drive.

By the end of this tutorial, you will be able to:

• Understand the fundamental concepts of File I/O
• Implement basic File I/O operations in your C# applications

This tutorial assumes that you have a basic understanding of C# programming. If you're new to C#, you might want to check out some beginner tutorials first.

2. Step-by-Step Guide

C# provides the System.IO namespace which contains types that allow reading and writing to files and data streams, and types that provide basic file and directory support.

Here are some of the commonly used classes in the System.IO namespace:

• FileStream: This class helps in reading from, writing to and closing files.
• StreamReader / StreamWriter: These classes are used for reading from and writing to character-based streams.
• BinaryReader / BinaryWriter: These classes are used for reading from and writing to binary streams.

Best Practices

• Always close the file after performing operations. You can use the Dispose method or a using statement to automatically close the file when you're done with it.
• Handle exceptions when performing file operations. This will prevent your program from crashing if a file operation fails.

3. Code Examples

Example 1: Writing to a File

using System.IO;

string path = @"C:\temp\MyTest.txt";

// Create a file to write to.
using (StreamWriter sw = File.CreateText(path))
{
    sw.WriteLine("Hello");
    sw.WriteLine("And");
    sw.WriteLine("Welcome");
}

In this example, we are creating a text file and writing some lines to it.

• StreamWriter is the class used to write characters to a stream.
• File.CreateText creates or opens a file for writing UTF-8 encoded text.
• sw.WriteLine is the method used to write a string followed by a line terminator to the text string or stream.

Example 2: Reading from a File

using System.IO;

string path = @"C:\temp\MyTest.txt";

// Open the file to read from.
using (StreamReader sr = File.OpenText(path))
{
    string s;
    while ((s = sr.ReadLine()) != null)
    {
        Console.WriteLine(s);
    }
}

In this example, we are reading the lines from the previously created text file.

• StreamReader is the class used to read characters from a byte stream.
• File.OpenText opens an existing UTF-8 encoded text file for reading.
• sr.ReadLine reads a line of characters from the current stream and returns the data as a string.

4. Summary

In this tutorial, we have covered the basics of File I/O in C#. We've learned how to create a text file, write to a file, and read from a file.

As next steps, you can explore more complex operations such as appending to a file, reading and writing binary files, and working with directories.

5. Practice Exercises

Exercise 1: Create a program that writes the numbers 1 to 10 in a text file.

Exercise 2: Create a program that reads the file created in Exercise 1 and prints the numbers to the console.

Exercise 3: Modify the program from Exercise 2 to handle exceptions if the file does not exist.

Happy coding!