InternalStreamReader FileAccess to ReadWrite

[LordPinhead]

Based on Issue #248, is there a reason not to change the FileStream Constructor to use FileShare.ReadWrite? I know i could use a Stream directly to avoid errors while Excel locks the file, but i whould think Reading should not be stopped because someone forgot to close the file. I try´d it with this Option and have no negative impacts other than "The File could be changed by Excel while reading", that is the only downside i can think of.

[netniV]

@LordPinhead: I have an workaround with an FileStream an StreamAccess ReadWrite, so i can open it. I opened an Issue on Github to ask if there is any reason not doing this by default.

using (var stream = new FileStream(DataFile.FullName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
  using (var reader = new StreamReader(stream)) {
    engine.ReadStream(reader).ToList().ForEach(record => {
      // Do Something
    });
  }

I'll be honest, I'm surprised that works given that Excel has a write lock already on it. My text editors that handle locking (marking the file as readonly) for most scenarios won't even open an Excel locked file.

FileShare.Read is the default for those FileStream constructors without a FileShare parameter so maybe they aren't specifying it either.

The only concern I would have is when another process has the ability to write to a file we are trying to read, that could lead to data corruption issues in what we are trying to read. So given this I, personally, wouldn't feel it's correct use that by default in most scenario's.

Links to what I read, though these are the .NET Framework, I think the same would apply to core.

https://docs.microsoft.com/en-us/dotnet/api/system.io.filestream.-ctor?view=netframework-4.8#System_IO_FileStream__ctor_Microsoft_Win32_SafeHandles_SafeFileHandle_System_IO_FileAccess_

https://docs.microsoft.com/en-us/dotnet/api/system.io.fileshare?view=netframework-4.8

[mcavigelli]

I'm not sure if I understand the suggestion: are you suggesting to change

FileHelpers/FileHelpers/Streams/InternalStreamReader.cs

Line 56 in 9b063df

FileAccess.Read,

        var stream = new FileStream(path,
            FileMode.Open,
            FileAccess.Read,        // old
            FileShare.Read,
            bufferSize,
            FileOptions.SequentialScan);

        var stream = new FileStream(path,
            FileMode.Open,
            FileAccess.ReadWrite,    // new
            FileShare.Read,
            bufferSize,
            FileOptions.SequentialScan);

Matthias

[netniV]

No, I think he was after the row below, FileShare to be read/write, so that other files can have a write lock.

[mcavigelli]

Thank you for your clarification. It is included.