OpenTween.OTWebClient.DownloadDataAsync C# (CSharp) Method

        public new Task<byte[]> DownloadDataAsync(Uri address)
        {
            return this.DownloadDataAsync(address, CancellationToken.None);
        }

        /// <summary>
        /// 指定された URL にある画像を非同期に取得するメソッド
        /// </summary>
        /// <param name="address">取得先の URL</param>
        /// <param name="force">キャッシュを使用せずに取得する場合は true</param>
        /// <returns>非同期に画像を取得するタスク</returns>
        public Task <MemoryImage> DownloadImageAsync(string address, bool force = false)
        {
            var cancelToken = this.cancelTokenSource.Token;

            return(Task.Factory.StartNew(() =>
            {
                Task <MemoryImage> cachedImageTask = null;
                lock (this.lockObject)
                {
                    if (force)
                    {
                        this.innerDictionary.Remove(address);
                    }

                    if (this.innerDictionary.ContainsKey(address) && !this.innerDictionary[address].IsFaulted)
                    {
                        cachedImageTask = this.innerDictionary[address];
                    }
                }

                if (cachedImageTask != null)
                {
                    return cachedImageTask;
                }

                cancelToken.ThrowIfCancellationRequested();

                using (var client = new OTWebClient()
                {
                    Timeout = 10000
                })
                {
                    var imageTask = client.DownloadDataAsync(new Uri(address), cancelToken).ContinueWith(t =>
                    {
                        MemoryImage image = null;
                        if (t.Status == TaskStatus.RanToCompletion)
                        {
                            image = MemoryImage.CopyFromBytes(t.Result);
                        }

                        if (t.Exception != null)
                        {
                            t.Exception.Handle(e => e is WebException);
                        }

                        // FIXME: MemoryImage.Dispose() が正しいタイミングで呼ばれるように修正すべき
                        return image;
                    }, cancelToken);

                    lock (this.lockObject)
                    {
                        this.innerDictionary[address] = imageTask;
                    }

                    return imageTask;
                }
            }, cancelToken).Unwrap());
        }