C#: Append some text to an existing file

Last update on December 20 2024 12:40:33 (UTC/GMT +8 hours)

Write a program in C# Sharp to append some text to an existing file.

Sample Solution:-

C# Sharp Code:

using System; // Importing the System namespace for basic functionalities
using System.IO; // Importing the System.IO namespace for file operations
using System.Text; // Importing the System.Text namespace for encoding

class filexercise3 // Declaring a class named filexercise3
{
    public static void Main() // Declaring the Main method
    {
        string fileName = @"mytest.txt"; // Initializing a string variable with the file name

        try // Starting a try block to catch exceptions
        {
            // Delete the file if it exists.
            if (File.Exists(fileName)) // Checking if the file exists
            {
                File.Delete(fileName); // If the file exists, delete it
            }
			
            // Displaying a message to append some text to an existing file
            Console.Write("\n\n Append some text to an existing file  :\n");
            Console.Write("--------------------------------------------\n");

            // Create the file and write initial content to it.
            using (StreamWriter fileStr = File.CreateText(fileName)) // Creating a StreamWriter to write text to the file
            {
                // Writing initial content to the file
                fileStr.WriteLine(" Hello and Welcome");
                fileStr.WriteLine(" It is the first content");
                fileStr.WriteLine(" of the text file mytest.txt");
            }

            // Reading and displaying the content of the file before appending
            using (StreamReader sr = File.OpenText(fileName)) // Opening a StreamReader to read the content of the file
            {
                string s = "";
                Console.WriteLine(" Here is the content of the file mytest.txt : ");
                while ((s = sr.ReadLine()) != null) // Looping through each line until the end of the file
                {
                    Console.WriteLine(s); // Displaying each line in the console
                }
                Console.WriteLine(""); // Adding a newline for formatting
            }

            // Appending a line at the end of the file
            using (System.IO.StreamWriter file = new System.IO.StreamWriter(@"mytest.txt", true)) // Appending to the existing file using StreamWriter
            {
                file.WriteLine(" This is the line appended at the last line."); // Appending a line to the file
            }

            // Reading and displaying the content of the file after appending
            using (StreamReader sr = File.OpenText(fileName)) // Opening a StreamReader again to read the updated content of the file
            {
                string s = "";
                Console.WriteLine(" Here is the content of the file after appending the text : ");
                while ((s = sr.ReadLine()) != null) // Looping through each line until the end of the file
                {
                    Console.WriteLine(s); // Displaying each line in the console
                }
                Console.WriteLine(""); // Adding a newline for formatting
            }
        }
        catch (Exception MyExcep) // Catching any exceptions that might occur
        {
            Console.WriteLine(MyExcep.ToString()); // Displaying the exception details if any
        }
    }
}

Sample Output:

Append some text to an existing file  :                                                                      
--------------------------------------------                                                                  
 Here is the content of the file mytest.txt :                                                                 
 Hello and Welcome                                                                                            
 It is the first content                                                                                      
 of the text file mytest.txt                                                                                  
     
 Here is the content of the file after appending the text :                                                   
 Hello and Welcome                                                                                            
 It is the first content                                                                                      
 of the text file mytest.txt                                                                                  
 This is the line appended at last line. 
 

Flowchart :

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