DirectoryLocker.cs

void Main()
{
	DirectoryLocker.Create(@"C:\X");
	DirectoryLocker.Create(@"C:\X");
}

public static class DirectoryLocker
{
	private static ConcurrentDictionary<string, FileStream> _lockFiles = new ConcurrentDictionary<string, FileStream>();

	public static DirectoryInfo Create(string path)
	{
		var directory = Directory.CreateDirectory(path);
		_lockFiles.GetOrAdd(path, folder => File.Create(Path.Combine(folder, "lock")));
		return directory;
	}
	
	public static void Create(params string[] paths)
	{
		foreach(var path in paths)
		{
			Create(path);
		}
	}
}