C# File Handling: Reading from and writing to files using C#

File handling is an essential aspect of programming in any language, including C#. In this blog post, we will explore how to read from and write to files using C#.

Reading from Files

Reading data from a file is a common requirement in many applications. C# provides several ways to accomplish this task.

One of the simplest methods is to use the StreamReader class, which allows you to read text from a file line by line.

using System;
using System.IO;

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

In the above example, we first specify the file path (data.txt) that we want to read from. Then, we create an instance of the StreamReader class and use the using statement to ensure that the file is properly closed after reading.

Inside the while loop, we read each line of the file using the ReadLine() method and print it to the console. The loop continues until there are no more lines to read.

Another way to read from files is by using the File class, which provides static methods for file-related operations. The ReadAllLines() method, for instance, allows you to read all lines of a text file at once:

using System;
using System.IO;

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

This code snippet demonstrates how to read all lines of a file into a string array using the ReadAllLines() method. We then iterate over the array and print each line to the console.

Writing to Files

In addition to reading from files, C# also provides various options for writing data to files. Let’s explore a couple of them.

One straightforward approach is to use the StreamWriter class, which allows you to write text to a file.

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "output.txt";
        
        using (StreamWriter sw = new StreamWriter(filePath))
        {
            sw.WriteLine("Hello, World!");
        }
    }
}

In this example, we specify the file path (output.txt) that we want to write to. We then create an instance of the StreamWriter class and use the using statement to ensure that the file is properly closed after writing.

Inside the using block, we use the WriteLine() method to write the text “Hello, World!” to the file. If the file doesn’t exist, it will be created; otherwise, the existing file will be overwritten.

Another way to write to files is by using the File class. The WriteAllText() method, for instance, allows you to write a string to a file:

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "output.txt";
        string content = "Hello, World!";
        
        File.WriteAllText(filePath, content);
    }
}

This code snippet demonstrates how to write a string to a file using the WriteAllText() method. We first specify the file path (output.txt) and the content that we want to write. The method takes care of creating or overwriting the file as necessary.

Conclusion

C# provides powerful and convenient features for file handling. In this blog post, we have explored how to read from and write to files using C#. Whether you need to process large amounts of data or simply save user input, understanding file handling in C# is crucial. By leveraging the StreamReader, StreamWriter, and File classes, you can easily work with files and incorporate file operations into your C# applications.