In C#, input and output (I/O) operations are essential for interacting with users, files, and other systems. These operations allow you to read data from various sources (like the console or files) and write data to them. C# provides several classes and methods to facilitate I/O operations, primarily through the System namespace.

1. Console I/O

The simplest form of I/O in C# is through the console, using the Console class. This class provides methods for reading from and writing to the console.

Writing Output to the Console

You can use the Console.Write and Console.WriteLine methods to output data to the console.

• Console.Write: Writes data to the console without a newline.
• Console.WriteLine: Writes data to the console and appends a newline at the end.

Example:

using System;

class Program
{
    static void Main()
    {
        Console.Write("Enter your name: "); // Prompt without newline
        Console.WriteLine("Hello, World!"); // Output with newline
    }
}

Reading Input from the Console

To read input from the console, you can use the Console.ReadLine method, which reads a line of text entered by the user.

Example:

using System;

class Program
{
    static void Main()
    {
        Console.Write("Enter your name: ");
        string name = Console.ReadLine(); // Read user input
        Console.WriteLine($"Hello, {name}!"); // Output greeting
    }
}

2. File I/O

C# provides various classes in the System.IO namespace for reading from and writing to files. The most commonly used classes for file I/O are File, StreamReader, and StreamWriter.

Writing to a File

You can use the StreamWriter class to write text to a file. It provides methods like Write and WriteLine.

Example:

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "output.txt"; // Specify the file path
        using (StreamWriter writer = new StreamWriter(filePath))
        {
            writer.WriteLine("Hello, World!"); // Write line to the file
            writer.Write("This is a text file."); // Write without newline
        }
        Console.WriteLine("Data written to file.");
    }
}

Reading from a File

You can use the StreamReader class to read text from a file. It provides methods like ReadLine and ReadToEnd.

Example:

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "output.txt"; // Specify the file path
        using (StreamReader reader = new StreamReader(filePath))
        {
            string content = reader.ReadToEnd(); // Read all content
            Console.WriteLine("File content:");
            Console.WriteLine(content); // Output the content to the console
        }
    }
}

3. Exception Handling in I/O Operations

When performing I/O operations, it's essential to handle exceptions that may arise, such as file not found, access denied, or other I/O errors. This can be done using try-catch blocks.

Example:

using System;
using System.IO;

class Program
{
    static void Main()
    {
        string filePath = "output.txt"; // Specify the file path
        
        try
        {
            using (StreamReader reader = new StreamReader(filePath))
            {
                string content = reader.ReadToEnd();
                Console.WriteLine("File content:");
                Console.WriteLine(content);
            }
        }
        catch (FileNotFoundException ex)
        {
            Console.WriteLine($"Error: {ex.Message}"); // Handle file not found
        }
        catch (UnauthorizedAccessException ex)
        {
            Console.WriteLine($"Error: {ex.Message}"); // Handle access denied
        }
        catch (Exception ex)
        {
            Console.WriteLine($"An error occurred: {ex.Message}"); // Handle other exceptions
        }
    }
}

4. Working with Other I/O Streams

C# also supports other types of streams for more advanced I/O operations, including:

• Binary File I/O: For reading and writing binary data using BinaryReader and BinaryWriter.
• Memory Streams: For working with data stored in memory using MemoryStream.
• Network Streams: For reading from and writing to network resources.

Summary

• Console I/O: Use Console.Write and Console.ReadLine for simple user interaction in the console application.
• File I/O: Use StreamWriter for writing to files and StreamReader for reading from files, both of which belong to the System.IO namespace.
• Exception Handling: Always implement error handling for I/O operations to manage potential issues like missing files or access restrictions.
• Advanced Streams: Explore other types of streams (e.g., binary, memory, and network streams) for more complex I/O operations.

Understanding input and output in C# is crucial for building interactive applications, handling data storage, and ensuring robust error management during data operations.