Question

I face weird problem with IOException on different servers. Here is my story:

I have win server (C#) that monitors folder for file changes. Also, a FTP server (WinSSHD) is pointed on same folder. When someone uploads a file WinService checks is write complete or not. If file is uploaded WinService renames it via File.Move method.

Is write complete check is made by File.Open method. Like this:

public static bool IsWriteComplete(string filePath)
{
    bool isWriteComplete;
    FileStream stream = null;
    try
    {
        stream = File.Open(filePath, FileMode.Open, FileAccess.Write, FileShare.ReadWrite|FileShare.Delete);
        isWriteComplete = true;
    }
    catch (IOException)
    {
        isWriteComplete = false;
    }
    catch (Exception ex)
    {
        isWriteComplete = false;
    }
    finally
    {
        if (stream != null) { stream.Close(); }
    }
    return isWriteComplete;
}

For some reason on one server it works perfectly (Win2003SP2) and on another one (Win2003SP1) is not working at all. The IsWriteComplete method says True, WinServer tries to move file and dies by IOException later. I haven’t found any references regarding such issue.

To fix the issue I replaced File.Open by File.Move.
Before:

stream = File.Open(filePath, FileMode.Open, FileAccess.Write, FileShare.ReadWrite|FileShare.Delete);

After:

File.Move(filePath, filePath);

And now it works on second server (Win2003SP1) and doesn’t work on first one (Win2003SP2).

Does anybody know why it works as such?

Answer 1

Found the root cause of the behavior.
There was different FTP service installed: Techia. For some reason Tectia doesn’t set write lock on uploading files. That’s why File.Open(filePath, FileAccess.Write) doesn’t throw IOException.