File IO Operations in C#

File Input/Output (IO) operations are essential for reading from and writing to files in C#. Understanding these operations is crucial for managing data persistence and file manipulation. This guide will explain five key File IO operations in C#.

1. Reading from a File

Reading from a file involves opening a file, reading its contents, and then closing the file. The File.ReadAllText method is commonly used to read the entire content of a file as a string.

Example

string filePath = "example.txt";
string fileContent = File.ReadAllText(filePath);
Console.WriteLine(fileContent);

In this example, the File.ReadAllText method reads the entire content of "example.txt" and stores it in the fileContent variable.

2. Writing to a File

Writing to a file involves creating or opening a file, writing data to it, and then closing the file. The File.WriteAllText method is used to write a string to a file.

Example

string filePath = "output.txt";
string content = "Hello, World!";
File.WriteAllText(filePath, content);

In this example, the File.WriteAllText method writes the string "Hello, World!" to "output.txt". If the file does not exist, it is created; if it does exist, its content is overwritten.

3. Appending to a File

Appending to a file involves adding new data to the end of an existing file without overwriting its content. The File.AppendAllText method is used for this purpose.

Example

string filePath = "log.txt";
string newEntry = "New log entry at " + DateTime.Now;
File.AppendAllText(filePath, newEntry + Environment.NewLine);

In this example, the File.AppendAllText method appends a new log entry to "log.txt". If the file does not exist, it is created.

4. Reading Lines from a File

Reading lines from a file involves reading the file line by line. The File.ReadAllLines method returns an array of strings, where each string represents a line from the file.

Example

string filePath = "data.txt";
string[] lines = File.ReadAllLines(filePath);
foreach (string line in lines)
{
    Console.WriteLine(line);
}

In this example, the File.ReadAllLines method reads each line from "data.txt" and stores them in the lines array.

5. Writing Lines to a File

Writing lines to a file involves writing an array of strings, where each string is written as a separate line in the file. The File.WriteAllLines method is used for this purpose.

Example

string filePath = "output.txt";
string[] lines = { "Line 1", "Line 2", "Line 3" };
File.WriteAllLines(filePath, lines);

In this example, the File.WriteAllLines method writes each string in the lines array as a separate line in "output.txt".