1. Introduction

This tutorial is designed to introduce you to the process of reading from and writing to text files in C#. We will be using the StreamReader and StreamWriter classes in C# to accomplish this.

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

• Understand the StreamReader and StreamWriter classes
• Read from text files
• Write to text files

Prerequisites

• Basic knowledge of C# programming language
• A text editor such as Visual Studio or Notepad++
• .NET Core installed on your machine

2. Step-by-Step Guide

In C#, we use the StreamReader class to read data from a text file, and StreamWriter to write data to a text file.

StreamReader Class

This class comes from the System.IO namespace and is used for reading characters from a byte stream in a particular encoding.

StreamWriter Class

This class is also part of the System.IO namespace and is used to write characters to a stream in a specific encoding.

3. Code Examples

Example 1: Reading from a Text File

Here's an example of how to read from a text file using StreamReader.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        using (StreamReader reader = new StreamReader("test.txt"))
        {
            string line;
            while ((line = reader.ReadLine()) != null)
            {
                Console.WriteLine(line);
            }
        }
    }
}

Explanation

• We start by creating a new instance of StreamReader, passing the name of the file we want to read from.
• Then, we use a while loop to read each line of the file until there are no more lines to read.
• Each line is then printed out to the console using Console.WriteLine().

Example 2: Writing to a Text File

Here's an example of how to write to a text file using StreamWriter.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        using (StreamWriter writer = new StreamWriter("test.txt"))
        {
            writer.WriteLine("Hello, world!");
        }
    }
}

Explanation

• We create a new instance of StreamWriter, passing the name of the file we want to write to.
• We then use the WriteLine() method to write a line of text to the file.

4. Summary

In this tutorial, we've covered how to read from and write to text files in C# using the StreamReader and StreamWriter classes. We learned that the StreamReader class is used for reading data from a text file and the StreamWriter class is used for writing data to a text file.

For further learning, you could explore the other methods available in these classes, such as ReadToEnd() and Write().

5. Practice Exercises

Exercise 1: Write a program that reads a text file and counts the number of lines in the file.

Exercise 2: Write a program that writes the numbers 1 to 10 on separate lines in a text file.

Solutions

Solution to Exercise 1

using System;
using System.IO;

class Program
{
    static void Main()
    {
        using (StreamReader reader = new StreamReader("test.txt"))
        {
            int lineCount = 0;
            while (reader.ReadLine() != null)
            {
                lineCount++;
            }
            Console.WriteLine("Number of lines: " + lineCount);
        }
    }
}

In this program, we read each line of the file and increment a counter for each line. The total count is then printed out.

Solution to Exercise 2

using System;
using System.IO;

class Program
{
    static void Main()
    {
        using (StreamWriter writer = new StreamWriter("test.txt"))
        {
            for(int i=1; i<=10; i++)
            {
                writer.WriteLine(i);
            }
        }
    }
}

In this program, we use a for loop to write the numbers 1 to 10 on separate lines in the file.