Read and Write a Text File in C#

File handling is a fundamental operation in programming. In this article, we will explore how to read text file and write text file in C#. By the end, you'll understand essential C# file handling techniques with examples of read write operations. Whether you're new to C# file input output or looking for a text file handling tutorial, this guide is perfect for you.

Understanding File Handling in C#

File handling in C# involves performing text file operations like reading and writing data. C# provides classes like File, StreamReader, and StreamWriter for seamless text file manipulation.

How to Read a Text File in C#

To read text file, C# offers multiple methods. Below are two popular approaches:

1. Using the File.ReadAllText Method

This method reads the entire content of a file into a string.

📄

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "example.txt";

        // Read the entire file content
        string content = File.ReadAllText(filePath);

        Console.WriteLine("File Content:");
        Console.WriteLine(content);
    }
}

2. Using the StreamReader Class

The StreamReader class allows for line-by-line reading, which is useful for large files.

📄

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "example.txt";

        // Read file line by line
        using (StreamReader reader = new StreamReader(filePath))
        {
            string line;
            while ((line = reader.ReadLine()) != null)
            {
                Console.WriteLine(line);
            }
        }
    }
}

How to Write a Text File in C#

Writing data to a text file is another crucial part of C# file handling. Below are two common methods:

1. Using the File.WriteAllText Method

This method writes a string to a file, overwriting its content if it already exists.

📄

using System;
using System.IO;

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

        // Write content to file
        File.WriteAllText(filePath, content);

        Console.WriteLine("File written successfully.");
    }
}

2. Using the StreamWriter Class

The StreamWriter class enables appending data or writing line-by-line.

📄

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "example.txt";

        // Write line by line to the file
        using (StreamWriter writer = new StreamWriter(filePath))
        {
            writer.WriteLine("Line 1");
            writer.WriteLine("Line 2");
        }

        Console.WriteLine("Data written successfully.");
    }
}

Combining Read and Write Operations in C#

You can easily combine read write operations to modify files. Here’s an example:

📄

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "example.txt";

        // Read content
        string content = File.ReadAllText(filePath);
        Console.WriteLine("Original Content:");
        Console.WriteLine(content);

        // Modify and write back
        string updatedContent = content + "\nAdditional Line";
        File.WriteAllText(filePath, updatedContent);

        Console.WriteLine("Content updated successfully.");
    }
}

Best Practices for File Handling in C#

• Always handle exceptions to avoid runtime errors.
• Use using statements to automatically close file streams.
• Validate file paths to prevent errors.
• Perform necessary checks (e.g., File.Exists) before accessing files.

Conclusion

This guide has provided a comprehensive overview of C# file handling. By understanding read text file and write text file operations, you can efficiently manipulate files in your applications. The examples shared here highlight essential text file operations with practical use cases. Explore more about C# read write file methods to enhance your skills.

FAQs

1. How do I check if a file exists before reading it in C#?

Use the File.Exists method to verify file existence. Example: if (File.Exists(filePath)).

2. What is the difference between File.WriteAllText and StreamWriter?

File.WriteAllText overwrites the entire file content in one step, while StreamWriter allows for more control, such as appending or writing line-by-line.

3. How do I append data to an existing file in C#?

Use the StreamWriter class with the append parameter set to true:

📄

using (StreamWriter writer = new StreamWriter(filePath, true))
{
    writer.WriteLine("Appended Line");
}

4. Can I handle binary files with the same methods?

No, binary files require classes like FileStream or BinaryReader and BinaryWriter for appropriate handling.

5. What are the performance considerations for handling large files?

For large files, prefer line-by-line reading with StreamReader and buffered writing with StreamWriter to minimize memory usage.