/// <summary>
        /// Search video.
        /// </summary>
        /// <param name="keyword">The keyword.</param>
        /// <param name="resultCount">The count of result itmes.</param>
        /// <param name="sortBy">The way to order results.</param>
        /// <returns>The result items.</returns>
        /// <remarks>Now, the max count of items Google given is <b>64</b>.</remarks>
        public IList<IVideoResult> Search(string keyword, int resultCount, string sortBy)
        {
            if (keyword == null)
            {
                throw new ArgumentNullException("keyword");
            }

            var request = new GvideoSearchRequest { Query = keyword, SortBy = sortBy };
            return this.Search<GvideoResult, IVideoResult>(request, resultCount);
        }
        /// <summary>
        /// Begins an asynchronous request for searching video.
        /// </summary>
        /// <param name="keyword">The keyword.</param>
        /// <param name="resultCount">The count of result itmes.</param>
        /// <param name="sortBy">The way to order results.</param>
        /// <param name="callback">The <see cref="AsyncCallback"/> delegate.</param>
        /// <param name="state">An object containing state information for this asynchronous request.</param>
        /// <returns>An <see cref="IAsyncResult"/> that references the asynchronous request.</returns>
        public IAsyncResult BeginSearch(string keyword, int resultCount, string sortBy, AsyncCallback callback, object state)
        {
            if (keyword == null)
            {
                throw new ArgumentNullException("keyword");
            }

            var request = new GvideoSearchRequest { Query = keyword, SortBy = sortBy };
            return this.BeginSearch<GvideoResult>(request, resultCount, callback, state);
        }