How can you read a file while it is being written to by another process?

Question

ICSM Computer · Answer

To read a file while it is being written to by another process in C#, you need to open it with
shared read access. This lets your code read from the file even if another process has it open for writing — assuming that process allows sharing.
Example: Open file with shared access
using System;
using System.IO;
using System.Text;
class Program
{
    static void Main()
    {
        string path = @"C:\Logs\active.log";
        try
        {
            using (var stream = new FileStream(
                path,
                FileMode.Open,
                FileAccess.Read,
                FileShare.ReadWrite)) // andlt;-- allow reading even if another process is writing
            using (var reader = new StreamReader(stream, Encoding.UTF8))
            {
                string content = reader.ReadToEnd();
                Console.WriteLine(content);
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("Error reading file: " + ex.Message);
        }
    }
}
Key Points:
Option
Meaning
FileAccess.Read
You're only reading the file
FileShare.ReadWrite
Allows other processes to read/write while you read
FileMode.Open
Open the file (throws if it doesn't exist)
This works only if the other process opens the file with a compatible sharing mode.
Tip for reading tailing logs:
If the file is being appended to (like a log), you can use a while loop to poll for new content, similar to
tail -f.

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How can you read a file while it is being written to by another process?

ICSM Computer

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1 Answers

Example: Open file with shared access

Key Points:

Tip for reading tailing logs:

Liked By

Option	Meaning
`FileAccess.Read`	You're only reading the file
`FileShare.ReadWrite`	Allows other processes to read/write while you read
`FileMode.Open`	Open the file (throws if it doesn't exist)