C# - Write To a File and Read It

Writing file in C#

In the following example, we use the WriteAllText() method to create a file named "filename.txt" and write some content to it. Then we use the ReadAllText() method to read the contents of the file.

How to write a file in C#

1. Using File.WriteAllText

This method writes a string to a text file. If the file does not exist, it creates a new one; if it exists, the content is overwritten.

using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "example.txt";
        string content = "Hello, this is a sample text.";

        File.WriteAllText(filePath, content);
        Console.WriteLine("File written successfully!");
    }
}

2. Using File.AppendAllText

This method appends a string to a text file. If the file does not exist, it creates a new one.

using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "example.txt";
        string content = "Appending this line to the file.\n";

        File.AppendAllText(filePath, content);
        Console.WriteLine("Text appended successfully!");
    }
}

3. Using StreamWriter
The StreamWriter class provides more control over file writing. It can write line-by-line and can also be used with using statements to automatically close the file.

using System.IO;

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

        using (StreamWriter writer = new StreamWriter(filePath))
        {
            writer.WriteLine("Line 1: Hello World!");
            writer.WriteLine("Line 2: Writing to a file using StreamWriter.");
        }

        Console.WriteLine("File written using StreamWriter.");
    }
}