/// <summary>
        /// Get files of the directory.
        /// </summary>
        /// <param name="parentId">The id of the parent directory.</param>
        /// <returns></returns>
        public static List <DirectoryItem> GetFiles(string parentId)
        {
            var items = new List <DirectoryItem>();
            var fs    = GoogleDriveAPI.GetFiles(parentId);

            foreach (var file in fs.Files)
            {
                var newItem = new DirectoryItem()
                {
                    Name = file.Name,
                    Id   = file.Id,
                    Type = DirectoryItemType.File,
                };
                items.Add(newItem);
            }

            return(items);
        }
        /// <summary>
        /// Get directories of the directory.
        /// </summary>
        /// <param name="parentId">The id of the parent directory.</param>
        /// <returns></returns>
        public static List <DirectoryItem> GetDirectories(string parentId)
        {
            var items = new List <DirectoryItem>();
            var dirs  = GoogleDriveAPI.GetDirectories(parentId);

            foreach (var folder in dirs.Files)
            {
                var newItem = new DirectoryItem()
                {
                    Name = folder.Name,
                    Id   = folder.Id,
                    Type = DirectoryItemType.Folder,
                };
                items.Add(newItem);
            }

            return(items);
        }