Apprendre Safe File Operations | Safe File Operations and Debugging

When you work with files in C#, you often need to read from or write to files on disk. However, file operations are not always straightforward—many things can go wrong. For example, the file you want to read might not exist, or there could be a problem with the disk itself. Two common exceptions you will encounter are FileNotFoundException, which occurs when a file cannot be found, and IOException, which covers a wide range of input/output errors. Understanding how to anticipate and handle these exceptions is essential for writing robust programs.

Definition

An IO exception (IOException) is an error that occurs during input or output operations, such as reading from or writing to a file. File operations are error-prone because files might not exist, permissions might be insufficient, or hardware might fail, making it essential to handle these exceptions.

Program.cs


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using System;
using System.IO;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string path = "data.txt";
            try
            {
                string content = File.ReadAllText(path);
                Console.WriteLine("File content:");
                Console.WriteLine(content);
            }
            catch (FileNotFoundException)
            {
                Console.WriteLine("Error: The file was not found.");
            }
            catch (IOException ex)
            {
                Console.WriteLine($"An I/O error occurred: {ex.Message}");
            }
        }
    }
}

When accessing files, you should always follow best practices to avoid resource leaks and unpredictable errors. One of the most important habits is to use a using statement when working with file streams. This ensures that the file is properly closed and resources are released, even if an exception occurs. Additionally, always validate file paths and check for file existence before attempting to read or write, and handle exceptions with clear, user-friendly messages.

WritingExample.cs


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using System;
using System.IO;

namespace ConsoleApp
{
    public class WritingExample
    {
        public void WriteToFile(string path, string text)
        {
            try
            {
                using (StreamWriter writer = new StreamWriter(path))
                {
                    writer.WriteLine(text);
                }
            }
            catch (IOException ex)
            {
                Console.WriteLine($"Could not write to file: {ex.Message}");
            }
        }
    }
}

This code defines a class that writes text to a file at a specified path. It uses a StreamWriter inside a using block to ensure the file resource is properly closed after writing. If a file-related error occurs during the operation, the code catches an IOException and outputs a descriptive error message to the console.

1. What exception is thrown if a file does not exist?

2. Why should you use try-catch when working with files?

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Section 4. Chapitre 1

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