C# Program to make a copy of an existing file

The File.Copy method in C# is used to copy an existing file from one location to another. This method is part of the System.IO namespace and provides a simple way to duplicate files programmatically.

Syntax

Following is the syntax for the File.Copy method −

File.Copy(string sourceFileName, string destFileName);
File.Copy(string sourceFileName, string destFileName, bool overwrite);

Parameters

• sourceFileName − The path of the file to copy.

• destFileName − The path of the destination file.

• overwrite − Optional boolean parameter. If true, overwrites the destination file if it already exists.

Using File.Copy to Copy a File

Here's a basic example of copying a file from one location to another −

using System;
using System.IO;

public class Program {
    public static void Main() {
        string sourcePath = @"D:\source.txt";
        string destinationPath = @"D:\copy.txt";
        
        // Create a sample file first
        File.WriteAllText(sourcePath, "This is the original file content.");
        
        // Copy the file
        File.Copy(sourcePath, destinationPath);
        
        Console.WriteLine("File copied successfully!");
        Console.WriteLine("Source: " + sourcePath);
        Console.WriteLine("Destination: " + destinationPath);
        
        // Verify the copy by reading content
        string copiedContent = File.ReadAllText(destinationPath);
        Console.WriteLine("Copied file content: " + copiedContent);
    }
}

The output of the above code is −

File copied successfully!
Source: D:\source.txt
Destination: D:\copy.txt
Copied file content: This is the original file content.

Using File.Copy with Overwrite Option

When the destination file already exists, you need to specify the overwrite parameter −

using System;
using System.IO;

public class Program {
    public static void Main() {
        string sourcePath = @"D:\original.txt";
        string destinationPath = @"D:\backup.txt";
        
        // Create source file
        File.WriteAllText(sourcePath, "Updated content for backup.");
        
        // Create destination file that already exists
        File.WriteAllText(destinationPath, "Old backup content.");
        
        try {
            // Copy with overwrite enabled
            File.Copy(sourcePath, destinationPath, true);
            Console.WriteLine("File copied and overwritten successfully!");
            
            string newContent = File.ReadAllText(destinationPath);
            Console.WriteLine("New backup content: " + newContent);
        }
        catch (Exception ex) {
            Console.WriteLine("Error: " + ex.Message);
        }
    }
}

The output of the above code is −

File copied and overwritten successfully!
New backup content: Updated content for backup.

Handling Exceptions

It's important to handle potential exceptions when copying files −

using System;
using System.IO;

public class Program {
    public static void Main() {
        string sourcePath = @"D:\document.txt";
        string destinationPath = @"D:\document_copy.txt";
        
        try {
            // Create source file for demonstration
            File.WriteAllText(sourcePath, "Important document content.");
            
            // Check if source file exists
            if (File.Exists(sourcePath)) {
                File.Copy(sourcePath, destinationPath);
                Console.WriteLine("File copied successfully!");
                Console.WriteLine("File size: " + new FileInfo(destinationPath).Length + " bytes");
            }
            else {
                Console.WriteLine("Source file does not exist.");
            }
        }
        catch (UnauthorizedAccessException) {
            Console.WriteLine("Access denied. Check file permissions.");
        }
        catch (DirectoryNotFoundException) {
            Console.WriteLine("Directory not found. Check the path.");
        }
        catch (IOException ex) {
            Console.WriteLine("IO Error: " + ex.Message);
        }
    }
}

The output of the above code is −

File copied successfully!
File size: 27 bytes

Common Use Cases

• Backup creation − Creating backups of important files before modifications.

• File distribution − Copying files to multiple locations for distribution.

• Template duplication − Creating copies of template files for customization.

• Data migration − Moving files during system upgrades or migrations.

Conclusion

The File.Copy method provides a straightforward way to duplicate files in C#. Remember to handle exceptions properly and use the overwrite parameter when the destination file might already exist. Always verify that the source file exists before attempting to copy it.