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Week 4: Files, Directories, and I/O in C#


⁠

🔹 1. File Handling Basics

Key Classes for File Operations:
File (high-level): Provides easy, static methods for quick file operations.
Common Methods:
File.Exists("path"): Checks if a file exists.
File.Delete("path"): Deletes the file.
File.Copy("source", "destination"): Copies a file to a new location.
FileStream (low-level): Allows byte-level control over file access and operations.
⁠

🔹 2. Reading and Writing Files

🔸 Reading from Files

File.ReadAllText("path"): Reads the entire file content as a string.
StreamReader: Reads text files line-by-line, useful for large files.
Example:
csharp
Copy code
using (StreamReader reader = new StreamReader("file.txt"))
{
while (!reader.EndOfStream)
{
Console.WriteLine(reader.ReadLine());
}
}

🔸 Writing to Files

File.WriteAllText("path", "text"): Writes text to a file, overwriting existing content.
File.AppendAllText("path", "text"): Appends text to an existing file.
StreamWriter: Writes to a file, line-by-line if needed.
Example:
csharp
Copy code
using (StreamWriter writer = new StreamWriter("file.txt"))
{
writer.WriteLine("Hello, World!");
}

⁠

🔹 3. Directory Management

Checking Directory Existence: Directory.Exists("path")
Creating a Directory: Directory.CreateDirectory("path")
Getting Directory Metadata: Use DirectoryInfo for details like creation and modification dates.
Example:
csharp
Copy code
DirectoryInfo info = new DirectoryInfo("path");
Console.WriteLine(info.CreationTime);

⁠

🔹 4. Path Operations

Path Class: Simplifies file and directory path management.
Common Methods:
Path.Combine("folder", "file.txt"): Combines folder and file names into a full path.
Path.GetExtension("file.txt"): Returns the file extension, e.g., .txt
Path.GetFileNameWithoutExtension("file.txt"): Returns the file name without extension, e.g., file
⁠

🔹 5. Working Directory

Getting Current Directory:
Environment.CurrentDirectory: Returns the current directory path.
Directory.GetCurrentDirectory(): Also retrieves the current working directory.
⁠

🔹 6. Exception Handling in File Operations

Common Exceptions

FileNotFoundException: Triggered when trying to read a non-existent file.
DirectoryNotFoundException: Triggered if a specified directory does not exist.
IOException: A general I/O exception, often caused by access conflicts.

Best Practice: Always handle exceptions in file I/O to prevent crashes.

Example:
csharp
Copy code
try
{
string text = File.ReadAllText("file.txt");
}
catch (FileNotFoundException e)
{
Console.WriteLine("File not found.");
}

⁠

🔹 7. Using using Statement for Resource Management

Purpose: Ensures proper disposal of resources (like file streams) after use.
Syntax:
csharp
Copy code
using (StreamReader reader = new StreamReader("file.txt"))
{
// Perform file reading
} // StreamReader is automatically closed here

⁠

🔹 8. Summary of Key Classes and Methods

Table 16
Class
Purpose
Common Methods
1
File
High-level file management
Exists, ReadAllText, WriteAllText
2
FileStream
Low-level byte-based file operations
Open, Close
3
StreamReader
Text-based file reading
ReadLine, ReadToEnd
4
StreamWriter
Text-based file writing
Write, WriteLine
5
Directory
High-level directory management
Exists, CreateDirectory
6
DirectoryInfo
Directory metadata
Creation time, last access time
7
Path
Path management helper
Combine, GetExtension, GetFileName
There are no rows in this table
⁠
⁠

✨ Quick Tips for Exam Prep

Remember using statement: Essential for managing resources automatically.
Know the key classes:
High-level (easier): File, Directory
Low-level (more control): FileStream
Common Exceptions: FileNotFoundException, DirectoryNotFoundException, IOException — make sure to practice handling these.

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