Working with Files

Part of the Logic & Flow section of Coddy's C# journey — lesson 26 of 66.

In C#, you can work with files using classes from the System.IO namespace. The two main classes for text files are StreamReader (for reading) and StreamWriter (for writing).

Writing to a file:

using System.IO;

// Create a StreamWriter to write to a file
StreamWriter writer = new StreamWriter("myfile.txt");

// Write text to the file
writer.WriteLine("Hello, World!");
writer.WriteLine("This is line 2");

// Close the file
writer.Close();

Reading from a file:

using System.IO;

// Create a StreamReader to read from a file
StreamReader reader = new StreamReader("myfile.txt");

// Read all content from the file
string content = reader.ReadToEnd();
Console.WriteLine(content);

// Close the file
reader.Close();

Reading line by line:

StreamReader reader = new StreamReader("myfile.txt");

// Read first line
string line1 = reader.ReadLine();
Console.WriteLine(line1);

// Read second line
string line2 = reader.ReadLine();
Console.WriteLine(line2);

reader.Close();

Remember to always close your files with Close() when you're done!

Challenge

Easy

Create a method named ReadFile that:

Takes one string parameter: filename
Reads the content from the file using StreamReader
Prints the content to the console
Closes the reader

Cheat sheet

Work with files using the System.IO namespace. Use StreamWriter to write and StreamReader to read.

Writing to a file:

StreamWriter writer = new StreamWriter("myfile.txt");
writer.WriteLine("Hello, World!");
writer.Close();

Reading from a file:

StreamReader reader = new StreamReader("myfile.txt");
string content = reader.ReadToEnd();
Console.WriteLine(content);
reader.Close();

Reading line by line:

StreamReader reader = new StreamReader("myfile.txt");
string line = reader.ReadLine();
Console.WriteLine(line);
reader.Close();

Key methods:

WriteLine(text) - Write a line to the file
ReadToEnd() - Read all text from the file
ReadLine() - Read one line from the file
Close() - Close the file (always do this!)

Try it yourself

using System;
using System.IO;

class Program
{
    public static void ReadFile(string filename)
    {
        // Write your code here
    }
    
    static void Main(string[] args)
    {
        string filename = Console.ReadLine();
        ReadFile(filename);
    }
}