How do you prevent a file from being modified while reading it?

Question

ICSM Computer · Answer

To prevent a file from being modified while you are reading it in C#, you need to open it with
exclusive read access by using the appropriate FileShare mode.
Use FileShare.None to Deny Others Access
When you open the file for reading, specify FileShare.None so that
no other process can open the file (even for writing) while it's being read.
using System;
using System.IO;
class FileReadLockExample
{
    public static void ReadWithExclusiveLock(string filePath)
    {
        using (FileStream stream = new FileStream(
            filePath,
            FileMode.Open,
            FileAccess.Read,
            FileShare.None)) // No sharing allowed
        {
            using (StreamReader reader = new StreamReader(stream))
            {
                string content = reader.ReadToEnd();
                Console.WriteLine(content);
            }
        }
    }
}
FileShare Options Summary
FileShare Option
Meaning
None
Denies all other access (exclusive lock). ✅
Read
Allows others to read but not write.
Write
Allows others to write but not read.
ReadWrite
Allows others to read and write.
Delete
Allows others to delete the file.
Notes
Exclusive locks will throw an exception if another process tries to access the file.If you're in a multi-threaded app, you can use a lock or
Mutex in addition for thread-level synchronization.In real-time logging or shared file scenarios, consider using
FileShare.ReadWrite with retry logic instead.
Read More
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How do you prevent a file from being modified while reading it?

ICSM Computer

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1 Answers

Use `FileShare.None` to Deny Others Access

`FileShare` Options Summary

Notes

Liked By

FileShare Option	Meaning
`None`	Denies all other access (exclusive lock). ✅
`Read`	Allows others to read but not write.
`Write`	Allows others to write but not read.
`ReadWrite`	Allows others to read and write.
`Delete`	Allows others to delete the file.