Reading the file immediately after writing it, I get all zeros (.net)

Question

I have a program that should download files from a directory as soon as they are written. I received a FileSystemWatcher to notify me of directory changes. Instead of checking the event for what has changed, I just listed the files and started processing everything that I found.

In order not to try to read the file that is still being written, I have the code:

try {
    fs = fi.Open(FileMode.Open, FileAccess.ReadWrite,
                    FileShare.None);
    message = new byte[fs.Length];
    int br = fs.Read(message, 0, (int)fi.Length);
}
catch (Exception e) {
    // I'll get it next time around
    return;
}
finally {
    if (fs != null)
        fs.Close();
}

The problem is that for some files, about 1 in 200, the program reads all zeros. The file length is correct, but the content seems to be zero. When I check the last file, I find that it contains the actual correct data. I thought a way to open a file would prevent premature access to the file.

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Answer 2

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fi.Open(FileMode.Open, FileAccess.Read, FileShare.ReadWrite);

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