bool IsShortcut(string path)
        {
            string directory = Path.GetDirectoryName(path);
            string file = Path.GetFileName(path);

            //C:\Windows\system32\shell32.dll
            Shell32.Shell shell = new Shell32.Shell();
            Shell32.Folder folder = shell.NameSpace(directory);
            Shell32.FolderItem folderItem = folder.ParseName(file);

            if (folderItem != null)
            {
                return folderItem.IsLink;
            }

            return false;
        }

            System.IO.DirectoryInfo di = new System.IO.DirectoryInfo(@"c:\users\all users");
            if( (di.Attributes & System.IO.FileAttributes.ReparsePoint) !=0){
                // детали WinApi откроет
            }