C# Beyond Basics

Writing Files

For writing text in a file we create a StreamWriter object with the path of the file, similar to how we create a StreamReader object.

Note

The platform currently doesn't support file writing so this can be practiced on a compiler on your PC.

The StreamWriter object offers a WriteLine method which can write text into a file. We will now try to write something to the text.txt file.

index.cs

var textFile = new StreamWriter("C:/Users/Admin/Desktop/text.txt");

textFile.WriteLine("This is some new text.");

textFile.WriteLine("This is the next line.");

textFile.WriteLine("Another line.");

textFile.Close();


              12345
            
var textFile = new StreamWriter("C:/Users/Admin/Desktop/text.txt");
textFile.WriteLine("This is some new text.");
textFile.WriteLine("This is the next line.");
textFile.WriteLine("Another line.");
textFile.Close();

The above code will overwrite the previous content of the text.txt file and replace it with:


9
1
2
3
This is some new text.
This is the next line.
Another line.

StreamWriter has a second parameter called "append" which takes in a boolean value and is set to false by default. If we set the append parameter to true then the code will not overwrite the older text rather it would append the new text to the end of the file.

For-example, consider the file text.txt has the following text in it:

text.txt

First line

Second line

Third line


              123
            
First line
Second line
Third line

We will use the following code to add a new line to it:

index.cs

using System;

using System.IO;

public class HelloWorld

{

public static void Main(string[] args)

{

var textFile = new StreamWriter("C:/Users/Admin/Desktop/text.txt", true);

textFile.WriteLine("This is a new line.");

textFile.Close();

}


              123456789101112
            
using System;
using System.IO;

public class HelloWorld
{
    public static void Main(string[] args)
    {
        var textFile = new StreamWriter("C:/Users/Admin/Desktop/text.txt", true);
        textFile.WriteLine("This is a new line.");
        textFile.Close();
    }
}

The file will look like this after running the code:

text.txt

First line

Second line

Third line

This is a new line.


              1234
            
First line
Second line
Third line
This is a new line.

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Writing Files

1. What is the correct way of creating a StreamWriter object for appending text into a file?

2. What method is used to write a line to a text file using the StreamWriter class?

3. Which method is used for closing a file after use?