Does ReplaceFile fail with ERROR_SHARING_VIOLATION because of race condition?

Question

This is a simplification of a problem I encounter.

There are 2 process: one that loops over ReplaceFile

[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
static extern int ReplaceFile(string lpReplacedFileName, string lpReplacementFileName, string lpBackupFileName, uint dwReplaceFlags, IntPtr lpExclude, IntPtr lpReserved);

static void Main(string[] args)
{
    IntPtr lpExclude = new IntPtr();
    IntPtr lpReserved = new IntPtr();

    string pathA = @"C:\temp\a.txt";
    string pathB = @"C:\temp\b.txt";
    string pathC = @"C:\temp\c.txt";
    while (true)
    {
        if (ReplaceFile(pathA, pathB, pathC, 0, lpExclude, lpReserved) == 0)
            Console.WriteLine(Marshal.GetLastWin32Error());
        if (ReplaceFile(pathA, pathC, pathB, 0, lpExclude, lpReserved) == 0)
            Console.WriteLine(Marshal.GetLastWin32Error());
    }
}

and another process that loops with open file to read with Read-Write-Delete permissions.

static void Main(string[] args)
{
    string pathB = @"C:\temp\b.txt";
    while (true) {
        try
        {
            FileStream fs = File.Open(pathB, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete);
            fs.Close();
        }
        catch (Exception e)
        {
            Console.WriteLine(e.Message);
        }
    }    
}

I expected that the process with the ReplaceFile loop will always succeed but once in a while it fails with ERROR_SHARING_VIOLATION (32). I'm trying not to interrupt the replace file loop but from this example it seems to be unavoidable.

Is there a way to try to open a file for read without ever triggering ERROR_SHARING_VIOLATION from the ReplaceFile function?

Answer 1

There is no good solution but hopefully this explanation will help someone in the future. This problem can be simplified further by having the second process just opening the file before the first.

static void Main(string[] args)
{
    string pathB = @"C:\temp\b.txt";
    FileStream fs = File.Open(pathB, FileMode.Open, FileAccess.Read, FileShare.ReadWrite | FileShare.Delete);
    Console.ReadLine();
    fs.Close();
}

In this case, ReplaceFile always fails because it needs exclusivity to the file - FileShare.None:

Declines sharing of the current file. Any request to open the file (by this process or another process) will fail until the file is closed.

So the only option for my original problem is to just minimize the harm by trying to close the file as fast as possible (or avoid opening it).