Silverlight并行下载与串行下载

ParallelDownloader 

   /// <summary>
    /// 并行资源下载器
    /// </summary>
    public sealed class ParallelDownloader : DownloadBase {

        /// <summary>
        /// 资源下载进度中触发
        /// </summary>
        public event DownloadProgressChangedEventHandler DownloadProgressChanged;

        /// <summary>
        /// 资源下载完成
        /// </summary>
        public event OpenReadCompletedEventHandler OpenReadCompleted;

        /// <summary>
        /// 当前进度百分比
        /// </summary>
        public static int ProgressPercentage { get; private set; }

        readonly static List<string> loadingUri = new List<string>();
        readonly static List<string> waitingUri = new List<string>();
        /// <summary>
        /// 获取当前正在下载的地址
        /// </summary>
        public static List<string> LoadingUri { get { return loadingUri; } }
        /// <summary>
        /// 获取等待下载地址队列
        /// </summary>
        public static List<string> WaitingUri { get { return waitingUri; } }

        /// <summary>
        /// 下载资源文件
        /// </summary>
        /// <param name="uri">资源相对地址<</param>
        /// <param name="userToken">资源参数</param>
        /// <param name="waitingTime">如果正在被下载,等待检测时间(单位:毫秒)</param>
        public void OpenReadAsync(string uri, object userToken, bool isWaiting, int waitingTime) {
            if (loadedUri.Contains(uri)) {
                Download(uri, userToken);
            } else {
                if (loadingUri.Contains(uri)) {
                    //假如该资源正被下载中,则需要等待,每隔1秒检测一次是否已下载完成
                    if (isWaiting) {
                        DispatcherTimer timer = new DispatcherTimer() { Interval = TimeSpan.FromMilliseconds(waitingTime) };
                        EventHandler handler = null;
                        timer.Tick += handler = (s, e) => {
                            if (loadedUri.Contains(uri)) {
                                timer.Stop();
                                timer.Tick -= handler;
                                Download(uri, userToken);
                            }
                        };
                        timer.Start();
                    }
                } else {
                    if (!waitingUri.Contains(uri)) { waitingUri.Add(uri); }
                    loadingUri.Add(uri);
                    Download(uri, userToken);
                }
            }
        }

        /// <summary>
        /// 开始下载
        /// </summary>
        /// <param name="uri">资源相对地址</param>
        /// <param name="userToken">资源参数</param>
        void Download(string uri, object userToken) {
            OpenReadCompletedEventHandler openReadCompletedHandler = null;
            DownloadProgressChangedEventHandler progressChangedHandler = null;
            WebClient webClient = new WebClient();
            webClient.DownloadProgressChanged += progressChangedHandler = (s, e) => {
                ProgressPercentage = e.ProgressPercentage;
                if (DownloadProgressChanged != null) { DownloadProgressChanged(this, e); }
            };
            webClient.OpenReadCompleted += openReadCompletedHandler = (s, e) => {
                WebClient wc = s as WebClient;
                wc.DownloadProgressChanged -= progressChangedHandler;
                wc.OpenReadCompleted -= openReadCompletedHandler;
                if (e.Error != null) {
                    //断网处理,5秒后重试
                    Error++;
                    GlobalMethod.SetTimeout(delegate {
                        Download(uri, userToken);
                    }, 5000);
                } else {
                    waitingUri.Remove(uri);
                    loadingUri.Remove(uri);
                    if (!loadedUri.Contains(uri)) { loadedUri.Add(uri); }
                    if (OpenReadCompleted != null) { OpenReadCompleted(this, e); }
                }
            };
            webClient.OpenReadAsync(new Uri(uri, UriKind.Relative), userToken);
        }
    }

SerialDownloader 

    /// <summary>
    /// 下载优先级
    /// </summary>
    public enum DownloadPriority {
        /// <summary>
        /// 最高
        /// </summary>
        Highest = 0,
        /// <summary>
        /// 高
        /// </summary>
        High = 1,
        /// <summary>
        /// 普通
        /// </summary>
        Normal = 2,
        /// <summary>
        /// 低
        /// </summary>
        Low = 3,
        /// <summary>
        /// 最低
        /// </summary>
        Lowest = 4,
    }

    /// <summary>
    /// 串行资源下载器
    /// </summary>
    public class SerialDownloader : DownloadBase {

        /// <summary>
        /// 资源下载完成
        /// </summary>
        public static event OpenReadCompletedEventHandler OpenReadCompleted;

        /// <summary>
        /// 资源下载进度中触发
        /// </summary>
        public static event DownloadProgressChangedEventHandler DownloadProgressChanged;

        /// <summary>
        /// 当前进度百分比
        /// </summary>
        public static int ProgressPercentage { get; private set; }

        static WebClient webClient = null;
        readonly static List<string> loadingUri = new List<string>();
        readonly static List<string> waitingUri = new List<string>();
        /// <summary>
        /// 获取当前正在下载的地址
        /// </summary>
        public static List<string> LoadingUri { get { return loadingUri; } }
        /// <summary>
        /// 获取等待下载地址队列
        /// </summary>
        public static List<string> WaitingUri { get { return waitingUri; } }

        /// <summary>
        /// 为Image图片控件设置图像源
        /// </summary>
        /// <param name="image">目标图片</param>
        /// <param name="uri">图像源地址</param>
        /// <param name="isWaiting">是否等待下载完成后再赋值</param>
        public static void SetImageSource(Image image, string uri, DownloadPriority priority, bool isWaiting) {
            if (loadedUri.Contains(uri)) {
                image.Source = GlobalMethod.GetWebImage(uri);
            } else {
                image.Source = null;
                AddUri(uri, priority);
                if (isWaiting) {
                    DispatcherTimer timer = new DispatcherTimer() { Interval = TimeSpan.FromMilliseconds(2000) };
                    EventHandler handler = null;
                    timer.Tick += handler = (s, e) => {
                        if (loadedUri.Contains(uri)) {
                            timer.Stop();
                            timer.Tick -= handler;
                            image.Source = GlobalMethod.GetWebImage(uri);
                        }
                    };
                    timer.Start();
                }
            }
        }

        /// <summary>
        /// 添加预备下载地址
        /// </summary>
        /// <param name="uri">图像源地址</param>
        public static void AddUri(string uri, DownloadPriority priority) {
            if (!waitingUri.Contains(uri)) { waitingUri.Insert((int)(((int)priority / 4d) * waitingUri.Count), uri); }
            if (loadingUri.Count == 0) {
                webClient = new WebClient();
                webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
                webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(webClient_OpenReadCompleted);
                webClient.OpenReadAsync(new Uri(GlobalMethod.WebPath(uri), UriKind.Relative), uri);
                loadingUri.Add(uri);
            }
        }

        static void webClient_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e) {
            WebClient wc = sender as WebClient;
            wc.DownloadProgressChanged -= webClient_DownloadProgressChanged;
            wc.OpenReadCompleted -= webClient_OpenReadCompleted;
            string uri = e.UserState.ToString();
            if (e.Error != null) {
                //断网处理,5秒后重试
                Error++;
                GlobalMethod.SetTimeout(delegate {
                    loadingUri.Remove(uri);
                    AddUri(uri, DownloadPriority.Highest);
                }, 5000);
            } else {
                loadingUri.Remove(uri);
                waitingUri.Remove(uri);
                loadedUri.Add(uri);
                if (waitingUri.Count > 0) { AddUri(waitingUri[0], DownloadPriority.Highest); }
                if (OpenReadCompleted != null) { OpenReadCompleted(sender, e); }
            }
        }

        static void webClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e) {
            ProgressPercentage = e.ProgressPercentage;
            if (DownloadProgressChanged != null) { DownloadProgressChanged(sender, e); }
        }

    }