[C#] Copying, Moving, and Deleting Files (Basic Operations of the File Class)

File system operations, such as creating file backups, moving processed files, or deleting unnecessary logs, are performed using the static methods of the System.IO.File class.

When performing these operations, exceptions (errors) can easily occur if the target file does not exist or if a file with the same name already exists at the destination. Therefore, it is standard practice to check beforehand using File.Exists.

Table of Contents

• Implementation Sample: Backup and Restoration of Daily Report
• Sample Code
• Execution Result (1st Run: File Exists)
• Execution Result (2nd Run: File Missing)
• Explanation and Technical Points
  1. File.Copy
  2. File.Delete
  3. File.Move

Implementation Sample: Backup and Restoration of Daily Report

The following code implements logic that switches behavior based on file existence:

• If the “Daily Report File (DailyReport.csv)” exists, it copies it to a backup folder and deletes the original.
• Conversely, if the original file is missing but a backup exists, it restores (moves) the file from the backup.

Sample Code

using System;
using System.IO;

public class Program
{
    public static void Main()
    {
        // Target file path
        string currentDir = Directory.GetCurrentDirectory();
        string sourceFile = Path.Combine(currentDir, "DailyReport.csv");
        
        // Backup destination path
        string backupDir = Path.Combine(currentDir, "Backup");
        string backupFile = Path.Combine(backupDir, "DailyReport_Bak.csv");

        // (Preparation) Create backup folder if it doesn't exist
        if (!Directory.Exists(backupDir))
        {
            Directory.CreateDirectory(backupDir);
        }

        // ---------------------------------------------------------
        // Case 1: Source file exists -> Backup and delete
        // ---------------------------------------------------------
        if (File.Exists(sourceFile))
        {
            Console.WriteLine("[Process Start] Source file found. Creating backup.");

            // 1. Copy file (source, destination, overwrite flag)
            // If overwrite: true, it overwrites even if a file with the same name exists
            File.Copy(sourceFile, backupFile, overwrite: true);
            Console.WriteLine($"Copy Complete: {Path.GetFileName(backupFile)}");

            // 2. Delete the original file
            File.Delete(sourceFile);
            Console.WriteLine("Deleted original file.");
        }
        // ---------------------------------------------------------
        // Case 2: Source file missing, but backup exists -> Restore
        // ---------------------------------------------------------
        else if (File.Exists(backupFile))
        {
            Console.WriteLine("[Process Start] Source file missing. Restoring from backup.");

            // 3. Move file (also acts as rename)
            // Move(source, destination)
            File.Move(backupFile, sourceFile);
            Console.WriteLine($"Restore Complete: {Path.GetFileName(sourceFile)}");
        }
        else
        {
            Console.WriteLine("[Error] Target file not found anywhere.");
            
            // Create a file for testing
            File.WriteAllText(sourceFile, "2025-12-25, No Anomalies");
            Console.WriteLine("Created test file. Please re-run.");
        }
    }
}

Execution Result (1st Run: File Exists)

[Process Start] Source file found. Creating backup.
Copy Complete: DailyReport_Bak.csv
Deleted original file.

Execution Result (2nd Run: File Missing)

[Process Start] Source file missing. Restoring from backup.
Restore Complete: DailyReport.csv

Explanation and Technical Points

1. File.Copy

Use the File.Copy(source, dest, overwrite) method. If you set the third argument overwrite to true, it will forcibly overwrite the destination file even if it already exists. If false (the default), an IOException will be thrown if a file with the same name exists.

2. File.Delete

Use the File.Delete(path) method. This permanently deletes the file at the specified path. It does not go to the Recycle Bin, so it cannot be restored. Use this with caution. Note that if you call this method when the file does not exist, no error will occur; it is simply ignored.

3. File.Move

Use the File.Move(source, dest) method. This is used not only for “moving” a file to a different directory but also for “renaming” a file within the same directory. In .NET Core 3.0 and later, you can specify overwrite: true as a third argument to overwrite the file at the destination if it exists.