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一个简单的利用 WebClient 异步下载的示例（四）
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接上一篇，我们继续优化它。
1. DownloadEntry 类
public class DownloadEntry
{
public string Url { get; set; }
public string Path { get; set; }
/// <summary>
/// 当前处理的数据
/// </summary>
public object Data { get; set; }
public DownloadEntry(string url, string savedPath)
: this(url, savedPath, null)
{
}
public DownloadEntry(string url, string savedPath, object data)
{
Url = url;
Path = savedPath;
Data = data;
}
}
2. 增加事件
/// <summary>
/// 当单个下载前的事件处理
/// </summary>
/// <param name="current">当前处理的数据，有可能为 NULL，请注意判断</param>
public delegate void WhenSingleDownloadingEventHandler(DownloadEntry current);
/// <summary>
/// 当全部下载完毕后的事件处理
/// </summary>
public delegate void WhenAllDownloadedEventHandler();
/// <summary>
/// 当下载错误时
/// </summary>
/// <param name="ex"></param>
public delegate void WhenDownloadingErrorEventHandler(Exception ex);
3. 提取出 SkyWebClient 的基类
/// <summary>
/// SkyWebClient 的基类
/// </summary>
public class SkyWebClientBase : INotifyPropertyChanged
{
#region 字段、属性
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string prop)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(prop));
}
}
/// <summary>
/// 当单个下载前的事件处理
/// </summary>
public event WhenSingleDownloadingEventHandler WhenSingleDownloading;
protected virtual void OnWhenSingleDownloading(DownloadEntry next)
{
if (WhenSingleDownloading != null)
{
WhenSingleDownloading(next);
}
}
/// <summary>
/// 当全部下载完毕后的事件处理
/// </summary>
public event WhenAllDownloadedEventHandler WhenAllDownloaded;
protected virtual void OnWhenAllDownloaded()
{
if (WhenAllDownloaded != null)
{
WhenAllDownloaded();
}
}
/// <summary>
/// 当全部下载完毕后的事件处理
/// </summary>
public event WhenDownloadingErrorEventHandler WhenDownloadingError;
protected virtual void OnWhenDownloadingError(Exception ex)
{
if (WhenDownloadingError != null)
{
WhenDownloadingError(ex);
}
}
bool _canChange = true;
public bool CanChange
{
get
{
return _canChange;
}
set
{
_canChange = value;
OnPropertyChanged("CanChange");
}
}
#endregion
}
4. SkyParallelWebClient
/// <summary>
/// 并行的 WebClient
/// </summary>
public class SkyParallelWebClient : SkyWebClientBase
{
ConcurrentQueue<DownloadEntry> OptionDataList = new ConcurrentQueue<DownloadEntry>(); //比如说：有 500 个元素
ConcurrentQueue<Task> ProcessingTasks = new ConcurrentQueue<Task>(); //当前运行中的
public int ParallelCount { get; set; }
private bool IsCompleted { get; set; }
private static object lockObj = new object();
/// <summary>
/// 构造函数
/// </summary>
/// <param name="downloadConfigs">要下载的全部集合，比如 N 多要下载的，N无限制</param>
/// <param name="parallelCount">单位内，并行下载的个数。切忌：该数字不能过大，否则可能很多文件因为 WebClient 超时，而导致乱文件（即：文件不完整）一般推荐 20 个左右</param>
public SkyParallelWebClient(IEnumerable<DownloadEntry> downloadConfigs, int parallelCount)
{
if (downloadConfigs == null)
{
throw new ArgumentNullException("downloadConfigs");
}
this.ParallelCount = parallelCount;
foreach (var item in downloadConfigs)
{
OptionDataList.Enqueue(item);
}
}
/// <summary>
/// 启动（备注：由于内部采用异步下载，所以方法不用加 Try 和返回值）
/// </summary>
public void Start()
{
System.Net.ServicePointManager.DefaultConnectionLimit = int.MaxValue;
StartCore();
}
protected void StartCore()
{
if (OptionDataList.Count <= )
{
if (!IsCompleted)
{
lock (lockObj)
{
if (!IsCompleted)
{
OnWhenAllDownloaded();
IsCompleted = true;
}
}
}
return;
}
while (OptionDataList.Count > && ProcessingTasks.Count <= ParallelCount)
{
DownloadEntry downloadEntry;
if (!OptionDataList.TryDequeue(out downloadEntry))
{
break;
}
var task = DownloadFileAsync(downloadEntry);
ProcessingTasks.Enqueue(task);
OnWhenSingleDownloading(downloadEntry);
}
}
private Task DownloadFileAsync(DownloadEntry downloadEntry)
{
using (WebClient webClient = new WebClient())
{
//set this to null if there is no proxy
webClient.Proxy = null;
webClient.DownloadFileCompleted += WebClient_DownloadFileCompleted;
return webClient.DownloadFileTaskAsync(new Uri(downloadEntry.Url), downloadEntry.Path);
}
}
private void WebClient_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
{
Task task;
ProcessingTasks.TryDequeue(out task);
StartCore();
}
}
public class DownloadEntry
{
public string Url { get; set; } public string Path { get; set; } /// <summary>
/// 当前处理的数据
/// </summary>
public object Data { get; set; } public DownloadEntry(string url, string savedPath)
: this(url, savedPath, null)
{ } public DownloadEntry(string url, string savedPath, object data)
{
Url = url;
Path = savedPath;
Data = data;
}
}
/// <summary>
/// 当单个下载前的事件处理
/// </summary>
/// <param name="current">当前处理的数据，有可能为 NULL，请注意判断</param>
public delegate void WhenSingleDownloadingEventHandler(DownloadEntry current); /// <summary>
/// 当全部下载完毕后的事件处理
/// </summary>
public delegate void WhenAllDownloadedEventHandler(); /// <summary>
/// 当下载错误时
/// </summary>
/// <param name="ex"></param>
public delegate void WhenDownloadingErrorEventHandler(Exception ex);
3. 提取出 SkyWebClient 的基类
/// <summary>
/// SkyWebClient 的基类
/// </summary>
public class SkyWebClientBase : INotifyPropertyChanged
{
#region 字段、属性
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string prop)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(prop));
}
}
/// <summary>
/// 当单个下载前的事件处理
/// </summary>
public event WhenSingleDownloadingEventHandler WhenSingleDownloading;
protected virtual void OnWhenSingleDownloading(DownloadEntry next)
{
if (WhenSingleDownloading != null)
{
WhenSingleDownloading(next);
}
}
/// <summary>
/// 当全部下载完毕后的事件处理
/// </summary>
public event WhenAllDownloadedEventHandler WhenAllDownloaded;
protected virtual void OnWhenAllDownloaded()
{
if (WhenAllDownloaded != null)
{
WhenAllDownloaded();
}
}
/// <summary>
/// 当全部下载完毕后的事件处理
/// </summary>
public event WhenDownloadingErrorEventHandler WhenDownloadingError;
protected virtual void OnWhenDownloadingError(Exception ex)
{
if (WhenDownloadingError != null)
{
WhenDownloadingError(ex);
}
}
bool _canChange = true;
public bool CanChange
{
get
{
return _canChange;
}
set
{
_canChange = value;
OnPropertyChanged("CanChange");
}
}
#endregion
}
4. SkyParallelWebClient
/// <summary>
/// 并行的 WebClient
/// </summary>
public class SkyParallelWebClient : SkyWebClientBase
{
ConcurrentQueue<DownloadEntry> OptionDataList = new ConcurrentQueue<DownloadEntry>(); //比如说：有 500 个元素
ConcurrentQueue<Task> ProcessingTasks = new ConcurrentQueue<Task>(); //当前运行中的
public int ParallelCount { get; set; }
private bool IsCompleted { get; set; }
private static object lockObj = new object();
/// <summary>
/// 构造函数
/// </summary>
/// <param name="downloadConfigs">要下载的全部集合，比如 N 多要下载的，N无限制</param>
/// <param name="parallelCount">单位内，并行下载的个数。切忌：该数字不能过大，否则可能很多文件因为 WebClient 超时，而导致乱文件（即：文件不完整）一般推荐 20 个左右</param>
public SkyParallelWebClient(IEnumerable<DownloadEntry> downloadConfigs, int parallelCount)
{
if (downloadConfigs == null)
{
throw new ArgumentNullException("downloadConfigs");
}
this.ParallelCount = parallelCount;
foreach (var item in downloadConfigs)
{
OptionDataList.Enqueue(item);
}
}
/// <summary>
/// 启动（备注：由于内部采用异步下载，所以方法不用加 Try 和返回值）
/// </summary>
public void Start()
{
System.Net.ServicePointManager.DefaultConnectionLimit = int.MaxValue;
StartCore();
}
protected void StartCore()
{
if (OptionDataList.Count <= )
{
if (!IsCompleted)
{
lock (lockObj)
{
if (!IsCompleted)
{
OnWhenAllDownloaded();
IsCompleted = true;
}
}
}
return;
}
while (OptionDataList.Count > && ProcessingTasks.Count <= ParallelCount)
{
DownloadEntry downloadEntry;
if (!OptionDataList.TryDequeue(out downloadEntry))
{
break;
}
var task = DownloadFileAsync(downloadEntry);
ProcessingTasks.Enqueue(task);
OnWhenSingleDownloading(downloadEntry);
}
}
private Task DownloadFileAsync(DownloadEntry downloadEntry)
{
using (WebClient webClient = new WebClient())
{
//set this to null if there is no proxy
webClient.Proxy = null;
webClient.DownloadFileCompleted += WebClient_DownloadFileCompleted;
return webClient.DownloadFileTaskAsync(new Uri(downloadEntry.Url), downloadEntry.Path);
}
}
private void WebClient_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
{
Task task;
ProcessingTasks.TryDequeue(out task);
StartCore();
}
}
/// <summary>
/// SkyWebClient 的基类
/// </summary>
public class SkyWebClientBase : INotifyPropertyChanged
{
#region 字段、属性 public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string prop)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(prop));
}
} /// <summary>
/// 当单个下载前的事件处理
/// </summary>
public event WhenSingleDownloadingEventHandler WhenSingleDownloading;
protected virtual void OnWhenSingleDownloading(DownloadEntry next)
{
if (WhenSingleDownloading != null)
{
WhenSingleDownloading(next);
}
} /// <summary>
/// 当全部下载完毕后的事件处理
/// </summary>
public event WhenAllDownloadedEventHandler WhenAllDownloaded;
protected virtual void OnWhenAllDownloaded()
{
if (WhenAllDownloaded != null)
{
WhenAllDownloaded();
}
} /// <summary>
/// 当全部下载完毕后的事件处理
/// </summary>
public event WhenDownloadingErrorEventHandler WhenDownloadingError;
protected virtual void OnWhenDownloadingError(Exception ex)
{
if (WhenDownloadingError != null)
{
WhenDownloadingError(ex);
}
} bool _canChange = true;
public bool CanChange
{
get
{
return _canChange;
}
set
{
_canChange = value;
OnPropertyChanged("CanChange");
}
} #endregion
}
/// <summary>
/// 并行的 WebClient
/// </summary>
public class SkyParallelWebClient : SkyWebClientBase
{
ConcurrentQueue<DownloadEntry> OptionDataList = new ConcurrentQueue<DownloadEntry>(); //比如说：有 500 个元素 ConcurrentQueue<Task> ProcessingTasks = new ConcurrentQueue<Task>(); //当前运行中的 public int ParallelCount { get; set; } private bool IsCompleted { get; set; } private static object lockObj = new object(); /// <summary>
/// 构造函数
/// </summary>
/// <param name="downloadConfigs">要下载的全部集合，比如 N 多要下载的，N无限制</param>
/// <param name="parallelCount">单位内，并行下载的个数。切忌：该数字不能过大，否则可能很多文件因为 WebClient 超时，而导致乱文件（即：文件不完整）一般推荐 20 个左右</param>
public SkyParallelWebClient(IEnumerable<DownloadEntry> downloadConfigs, int parallelCount)
{
if (downloadConfigs == null)
{
throw new ArgumentNullException("downloadConfigs");
}
this.ParallelCount = parallelCount;
foreach (var item in downloadConfigs)
{
OptionDataList.Enqueue(item);
}
} /// <summary>
/// 启动（备注：由于内部采用异步下载，所以方法不用加 Try 和返回值）
/// </summary>
public void Start()
{
System.Net.ServicePointManager.DefaultConnectionLimit = int.MaxValue;
StartCore();
} protected void StartCore()
{
if (OptionDataList.Count <= )
{
if (!IsCompleted)
{
lock (lockObj)
{
if (!IsCompleted)
{
OnWhenAllDownloaded();
IsCompleted = true;
}
}
}
return;
}
while (OptionDataList.Count > && ProcessingTasks.Count <= ParallelCount)
{
DownloadEntry downloadEntry;
if (!OptionDataList.TryDequeue(out downloadEntry))
{
break;
}
var task = DownloadFileAsync(downloadEntry);
ProcessingTasks.Enqueue(task);
OnWhenSingleDownloading(downloadEntry);
}
} private Task DownloadFileAsync(DownloadEntry downloadEntry)
{
using (WebClient webClient = new WebClient())
{
//set this to null if there is no proxy
webClient.Proxy = null;
webClient.DownloadFileCompleted += WebClient_DownloadFileCompleted;
return webClient.DownloadFileTaskAsync(new Uri(downloadEntry.Url), downloadEntry.Path);
}
} private void WebClient_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
{
Task task;
ProcessingTasks.TryDequeue(out task);
StartCore();
}
}
5. TaskDemo101
public static class TaskDemo101
{
public static string GetRandomUrl(Random rd)
{
string url1 = "http://www.xxx.me/Uploads/image/20130129/2013012920080761761.jpg";
string url2 = "http://www.xxx.me/Uploads/image/20121222/20121222230686278627.jpg";
string url3 = "http://www.xxx.me/Uploads/image/20120606/20120606222018461846.jpg";
string url4 = "http://www.xxx.me/Uploads/image/20121205/20121205224383848384.jpg";
string url5 = "http://www.xxx.me/Uploads/image/20121205/20121205224251845184.jpg"; string resultUrl;
int randomNum = rd.Next(, );
switch (randomNum)
{
case : resultUrl = url1; break;
case : resultUrl = url2; break;
case : resultUrl = url3; break;
case : resultUrl = url4; break;
case : resultUrl = url5; break;
default: throw new Exception("");
}
return resultUrl;
} public static string GetSavedFileFullName()
{
string targetFolderDestination = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "downloads\\images\\");
try
{
Directory.CreateDirectory(targetFolderDestination);
}
catch (Exception)
{
Console.WriteLine("创建文件夹失败！");
}
string targetFileDestination = Path.Combine(targetFolderDestination, string.Format("img_{0}{1}.png", DateTime.Now.ToString("yyyy-MM-dd_HH-mm-ss"), Guid.NewGuid().ToString()));
return targetFileDestination;
} public static async Task<bool> RunByHttpClient(SkyHttpClient skyHttpClient, int id)
{
var task = skyHttpClient.DownloadImage(GetRandomUrl(new Random()));
return await task.ContinueWith<bool>(t => {
File.WriteAllBytes(GetSavedFileFullName(), t.Result);
return true;
});
} public static void RunByWebClient(WebClient webClient, int id)
{
webClient.DownloadFileAsync(new Uri(GetRandomUrl(new Random())), GetSavedFileFullName());
}
}
6. Form1
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private List<int> GetDownloadIds()
{
List<int> ids = new List<int>();
for (int i = ; i <= ; i++)
{
ids.Add(i);
}
return ids;
}
private void WhenAllDownloading()
{
this.listBoxLog.Items.Insert(, string.Format("当前时间：{0}，准备开始下载...", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")));
//禁用按钮
EnableOrDisableButtons(false);
}
private void EnableOrDisableButtons(bool enabled)
{
this.btnRunByHttpClient.Enabled = enabled;
this.btnRunByWebClient.Enabled = enabled;
}
private void WhenSingleDownloading(int id)
{
this.listBoxLog.Items.Insert(, string.Format("当前时间：{0}，编号 {1} 准备开始下载...", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"), id));
}
private void WhenAllDownloaded()
{
this.listBoxLog.Items.Insert(, string.Format("当前时间：{0}，下载完毕！", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")));
//启用按钮
EnableOrDisableButtons(true);
}
private async void btnRunByHttpClient_Click(object sender, EventArgs e)
{
SkyHttpClient skyHttpClient = new SkyHttpClient();
try
{
WhenAllDownloading();
foreach (var id in GetDownloadIds())
{
bool singleDownloadSuccess = await TaskDemo101.RunByHttpClient(skyHttpClient, id);
WhenSingleDownloading(id);
}
WhenAllDownloaded();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message, "Download Error!");
}
}
private void btnRunByWebClient_Click(object sender, EventArgs e)
{
WhenAllDownloading();
var ids = GetDownloadIds();
List<DownloadEntry> downloadConfigs = new List<DownloadEntry>();
Random rd = new Random();
foreach (var id in ids)
{
downloadConfigs.Add(new DownloadEntry(TaskDemo101.GetRandomUrl(rd), TaskDemo101.GetSavedFileFullName(), id));
}
//搜索： Parallel WebClient
// 方案1
//SkyWebClient skyWebClient = new SkyWebClient(downloadConfigs, this.progressBar1);
//skyWebClient.WhenAllDownloaded += SkyWebClient_WhenAllDownloaded;
//skyWebClient.WhenSingleDownloading += SkyWebClient_WhenSingleDownloading;
//skyWebClient.WhenDownloadingError += SkyWebClient_WhenDownloadingError;
//skyWebClient.Start();
// 方案2（代码已经调整，无法恢复）
//ThreadPool.QueueUserWorkItem(new WaitCallback(AsyncRunSkyParallelWebClient), downloadConfigs);
// 方案3
SkyParallelWebClient skyParallelWebClient = new SkyParallelWebClient(downloadConfigs, );
skyParallelWebClient.WhenAllDownloaded += SkyWebClient_WhenAllDownloaded;
skyParallelWebClient.WhenSingleDownloading += SkyWebClient_WhenSingleDownloading;
skyParallelWebClient.WhenDownloadingError += SkyWebClient_WhenDownloadingError;
skyParallelWebClient.Start();
}
private void SkyWebClient_WhenDownloadingError(Exception ex)
{
MessageBox.Show("下载时出现错误： " + ex.Message);
}
private void SkyWebClient_WhenSingleDownloading(DownloadEntry current)
{
WhenSingleDownloading((int)current.Data);
}
private void SkyWebClient_WhenAllDownloaded()
{
btnRunByWebClient.Text = "用 WebClient 开始下载";
WhenAllDownloaded();
}
}
7. 运行截图：
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
} private List<int> GetDownloadIds()
{
List<int> ids = new List<int>();
for (int i = ; i <= ; i++)
{
ids.Add(i);
}
return ids;
} private void WhenAllDownloading()
{
this.listBoxLog.Items.Insert(, string.Format("当前时间：{0}，准备开始下载...", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")));
//禁用按钮
EnableOrDisableButtons(false);
} private void EnableOrDisableButtons(bool enabled)
{
this.btnRunByHttpClient.Enabled = enabled;
this.btnRunByWebClient.Enabled = enabled;
} private void WhenSingleDownloading(int id)
{
this.listBoxLog.Items.Insert(, string.Format("当前时间：{0}，编号 {1} 准备开始下载...", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"), id));
} private void WhenAllDownloaded()
{
this.listBoxLog.Items.Insert(, string.Format("当前时间：{0}，下载完毕！", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")));
//启用按钮
EnableOrDisableButtons(true);
} private async void btnRunByHttpClient_Click(object sender, EventArgs e)
{
SkyHttpClient skyHttpClient = new SkyHttpClient();
try
{
WhenAllDownloading();
foreach (var id in GetDownloadIds())
{
bool singleDownloadSuccess = await TaskDemo101.RunByHttpClient(skyHttpClient, id);
WhenSingleDownloading(id);
}
WhenAllDownloaded();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message, "Download Error!");
}
} private void btnRunByWebClient_Click(object sender, EventArgs e)
{
WhenAllDownloading();
var ids = GetDownloadIds();
List<DownloadEntry> downloadConfigs = new List<DownloadEntry>();
Random rd = new Random();
foreach (var id in ids)
{
downloadConfigs.Add(new DownloadEntry(TaskDemo101.GetRandomUrl(rd), TaskDemo101.GetSavedFileFullName(), id));
}
//搜索： Parallel WebClient
// 方案1
//SkyWebClient skyWebClient = new SkyWebClient(downloadConfigs, this.progressBar1);
//skyWebClient.WhenAllDownloaded += SkyWebClient_WhenAllDownloaded;
//skyWebClient.WhenSingleDownloading += SkyWebClient_WhenSingleDownloading;
//skyWebClient.WhenDownloadingError += SkyWebClient_WhenDownloadingError;
//skyWebClient.Start();
// 方案2（代码已经调整，无法恢复）
//ThreadPool.QueueUserWorkItem(new WaitCallback(AsyncRunSkyParallelWebClient), downloadConfigs);
// 方案3
SkyParallelWebClient skyParallelWebClient = new SkyParallelWebClient(downloadConfigs, );
skyParallelWebClient.WhenAllDownloaded += SkyWebClient_WhenAllDownloaded;
skyParallelWebClient.WhenSingleDownloading += SkyWebClient_WhenSingleDownloading;
skyParallelWebClient.WhenDownloadingError += SkyWebClient_WhenDownloadingError;
skyParallelWebClient.Start();
} private void SkyWebClient_WhenDownloadingError(Exception ex)
{
MessageBox.Show("下载时出现错误： " + ex.Message);
} private void SkyWebClient_WhenSingleDownloading(DownloadEntry current)
{
WhenSingleDownloading((int)current.Data);
} private void SkyWebClient_WhenAllDownloaded()
{
btnRunByWebClient.Text = "用 WebClient 开始下载";
WhenAllDownloaded();
} }
如图：
8. 总结
还算比较完美，唯独 下载完毕后，可能会多次调用事件，需要优化。
下载：https://files.cnblogs.com/files/Music/SkyParallelWebClient_v2018-09-18.rar
谢谢浏览！
