Reading and Writing Text Files in C#

Handling files is a fundamental aspect of many software applications. Whether you're logging information, processing data from external sources, or creating reports, working with text files becomes essential. In this article, we will thoroughly explore Reading and Writing Text Files in C#, including syntax, methods, best practices, and practical examples to help you implement robust file I/O operations in your C# applications.

Introduction to Reading and Writing Text Files in C#

C# provides a rich set of classes in the System.IO namespace to work with files. These include:

• File – Provides static methods for creating, copying, deleting, reading, and writing to files.
• StreamReader – Reads characters from a byte stream in a particular encoding.
• StreamWriter – Writes characters to a stream in a particular encoding.
• FileStream – For low-level file operations and binary read/write.

Basic Syntax for Reading and Writing Text Files in C#

Reading from a Text File

📄
string filePath = "example.txt";

if (File.Exists(filePath))
{
    string content = File.ReadAllText(filePath);
    Console.WriteLine(content);
}
else
{
    Console.WriteLine("File does not exist.");
}

Explanation:

• File.ReadAllText reads all content from a file into a single string.
• Always check if the file exists using File.Exists to prevent runtime errors.

Writing to a Text File

📄
string filePath = "output.txt";
string data = "This is a test message.";

File.WriteAllText(filePath, data);

Explanation:

• File.WriteAllText writes the entire string to the specified file.
• If the file exists, it will be overwritten.

Different Methods for Reading and Writing Text Files in C#

Using StreamReader to Read Line by Line

📄
using (StreamReader reader = new StreamReader("example.txt"))
{
    string line;
    while ((line = reader.ReadLine()) != null)
    {
        Console.WriteLine(line);
    }
}

Using StreamWriter to Append Data

📄
using (StreamWriter writer = new StreamWriter("output.txt", true))
{
    writer.WriteLine("Appended line at: " + DateTime.Now);
}

Advantages of StreamReader/StreamWriter:

• Better for large files as it handles the file line by line.
• More memory-efficient than loading the entire file at once.

Appending Text to Files in C#

If you want to add content to an existing file without overwriting:

📄
File.AppendAllText("log.txt", "New entry at " + DateTime.Now + Environment.NewLine);

Error Handling in Reading and Writing Text Files in C#

📄
try
{
    string data = File.ReadAllText("nonexistent.txt");
    Console.WriteLine(data);
}
catch (FileNotFoundException ex)
{
    Console.WriteLine("Error: File not found - " + ex.Message);
}
catch (IOException ex)
{
    Console.WriteLine("IO Exception: " + ex.Message);
}

Best Practices for Reading and Writing Text Files in C#

• Always use using statements to ensure proper disposal of file streams.
• Handle exceptions to avoid crashes and unexpected behavior.
• Use async file methods for non-blocking I/O in UI applications.
• Ensure appropriate file permissions when accessing system folders.

Working with Large Files

For very large files, prefer reading and writing in chunks to avoid memory overflow.

📄
using (FileStream fs = new FileStream("large.txt", FileMode.Open))
{
    byte[] buffer = new byte[1024];
    int bytesRead;
    while ((bytesRead = fs.Read(buffer, 0, buffer.Length)) > 0)
    {
        Console.WriteLine(Encoding.UTF8.GetString(buffer, 0, bytesRead));
    }
}

Table: Common File I/O Methods in C#

Conclusion

Mastering Reading and Writing Text Files in C# is essential for developers working on any application involving file storage or manipulation. By understanding the different approaches and following best practices, you can ensure your file I/O operations are efficient, safe, and scalable.