How do you perform transactional file writes (e.g., write to a temp file, then replace original)?

Question

Anubhav Kumar · Answer

To perform transactional file writes in C#, the safest pattern is to:
Write to a temporary fileFlush and close itReplace the original file with the temp file (atomically)
This ensures the original file remains intact in case of crashes or write errors.
Example: Transactional Write
using System;
using System.IO;
public class SafeFileWriter
{
    public static void WriteTransactional(string filePath, string content)
    {
        string tempFile = Path.GetTempFileName();
        try
        {
            // Write to temp file
            File.WriteAllText(tempFile, content);
            // Ensure temp file is flushed and closed
            File.SetAttributes(tempFile, FileAttributes.Normal);
            // Replace original file atomically
            File.Replace(tempFile, filePath, null, ignoreMetadataErrors: true);
        }
        catch
        {
            // Optional: clean up temp file if something goes wrong
            if (File.Exists(tempFile))
                File.Delete(tempFile);
            throw;
        }
    }
}
Usage
SafeFileWriter.WriteTransactional("config.ini", "Safe=Write
Enabled=True");
Notes
Aspect
Detail
Path.GetTempFileName()
Creates a secure temp file in the system temp folder
File.Replace()
Atomically replaces target file (only works on NTFS / Windows)
ignoreMetadataErrors: true
Ignores errors when copying attributes (like timestamps)
Cross-platform?
For Linux/macOS, manually delete and move temp file (see below)
Alternative for Non-Windows Platforms
If you're not on Windows (e.g., using Linux/macOS), File.Replace isn't supported. Use:
File.Delete(originalPath);             // Optional: ensure it's gone
File.Move(tempFilePath, originalPath); // Non-atomic
To reduce risk of failure:
Use FileStream with proper Flush() and Close()Place temp file in the same directory as target file to reduce cross-volume issues.

forum

How do you perform transactional file writes (e.g., write to a temp file, then replace original)?

ICSM Computer

Can you answer this question?

1 Answers

Example: Transactional Write

Usage

Notes

Alternative for Non-Windows Platforms

Liked By

Aspect	Detail
`Path.GetTempFileName()`	Creates a secure temp file in the system temp folder
`File.Replace()`	Atomically replaces target file (only works on NTFS / Windows)
`ignoreMetadataErrors: true`	Ignores errors when copying attributes (like timestamps)
Cross-platform?	For Linux/macOS, manually delete and move temp file (see below)