使用.net 2.0我需要实现一些线程，我正在查看一个虚拟示例，但找不到任何实现事件通知的内容。 需要知道什么时候完成，如果你愿意，也需要某种进度条。
我一直在玩以下代码无法正常获取事件通知。 我怎么检测到我已完成处理并可能用我正在做的事情更新ui？
示例代码
class Program
{
static void Main(string[] args)
{
using (PCQueue q = new PCQueue(2))
{
q.TaskCompleted += new EventHandler(OnTaskCompleted);
q.PercentageCompleted += new EventHandler(OnPercentageCompleted);
for (int i = 1; i < 100; i++)
{
string itemNumber = i.ToString(); // To avoid the captured variable trap
q.EnqueueItem(itemNumber);
}
Console.WriteLine("Waiting for items to complete...");
Console.Read();
}
}
private static void OnPercentageCompleted(object sender, EventArgs e)
{
}
static void OnTaskCompleted(object sender, EventArgs e)
{
}
}
public class PCQueue : IDisposable
{
readonly object locker = new object();
Thread[] _workers;
Queue<string> _itemQ = new Queue<string>();
public PCQueue(int workerCount)
{
_workers = new Thread[workerCount];
// Create and start a separate thread for each worker
for (int i = 0; i < workerCount; i++)
{
(_workers[i] = new Thread(Consume)).Start();
}
}
public void EnqueueItem(string item)
{
lock (locker)
{
_itemQ.Enqueue(item); // We must pulse because we're
Monitor.Pulse(locker); // changing a blocking condition.
}
}
void Consume()
{
while (true) // Keep consuming until
{ // told otherwise.
string item;
lock (locker)
{
while (_itemQ.Count == 0) Monitor.Wait(locker);
item = _itemQ.Dequeue();
}
if (item == null) return; // This signals our exit.
DoSomething(item); // Execute item.
}
}
private void DoSomething(string item)
{
Console.WriteLine(item);
}
public void Dispose()
{
// Enqueue one null item per worker to make each exit.
foreach (Thread worker in _workers)
{
EnqueueItem(null);
}
}
//where/how can I fire this event???
public event EventHandler TaskCompleted;
protected void OnCompleted(EventArgs e)
{
if (this.TaskCompleted != null)
{
this.TaskCompleted(this, e);
}
}
//where/how can I fire this event???
public event EventHandler PercentageCompleted;
protected void OnPercentageCompleted(EventArgs e)
{
if (this.PercentageCompleted != null)
{
this.PercentageCompleted(this, e);
}
}
}
有什么建议吗？
答案 0 :(得分：2)
您无法在队列中引发progress事件，原因很简单，因为队列不知道应该处理的项目总数。所以它无法计算百分比。你只需坚持一些东西就可以得到处理。
你可以做的是提出一个ItemProcessed事件并订阅它。然后在你的主程序中，你可以做一个逻辑，计算到目前为止处理的项目数与处理的数量有关。
您可以在从Consume功能返回之前提升完整事件。但是，正如布莱恩在回答中所说，你需要跟踪有多少线程仍处于活动状态。我修改了代码以反映出来。
这些内容如下：
...
private int _ActiveThreads;
public PCQueue(int workerCount)
{
_ActiveThreads = workerCount;
_workers = new Thread[workerCount];
// Create and start a separate thread for each worker
for (int i = 0; i < workerCount; i++)
{
(_workers[i] = new Thread(Consume)).Start();
}
}
void Consume()
{
while (true) // Keep consuming until
{ // told otherwise.
string item;
lock (locker)
{
while (_itemQ.Count == 0) Monitor.Wait(locker);
item = _itemQ.Dequeue();
}
if (item == null) // This signals our exit.
{
if (Interlocked.Decrement(ref _ActiveThreads) == 0)
{
OnCompleted(EventArgs.Empty);
}
return;
}
DoSomething(item); // Execute item.
OnItemProcessed();
}
}
public event EventHandler ItemProcessed;
protected void OnItemProcessed()
{
var handler = ItemProcessed;
if (handler != null)
{
handler(this, EventArgs.Empty);
}
}
...
当然，你可能想要创建一些有意义的事件args并实际传递处理到事件的项目。
然后在主要：
...
static void Main(string[] args)
{
using (PCQueue q = new PCQueue(2))
{
q.ItemProcessed += ItemProcessed;
q.TaskCompleted += OnTaskCompleted;
for (int i = 1; i <= totalNumberOfItems; i++)
{
string itemNumber = i.ToString(); // To avoid the captured variable trap
q.EnqueueItem(itemNumber);
}
Console.WriteLine("Waiting for items to complete...");
Console.Read();
}
}
private static int currentProcessCount = 0;
private static int totalNumberOfItems = 100;
private static void ItemProcessed(object sender, EventArgs e)
{
currentProcessCount++;
Console.WriteLine("Progress: {0}%", ((double)currentProcessCount / (double)totalNumberOfItems) * 100.0);
}
static void OnTaskCompleted(object sender, EventArgs e)
{
Console.WriteLine("Done");
}
...
毋庸置疑，所有静态的东西都应该去。这只是基于你的例子。
还有一句话：
您的PCQueue当前要求您将多个null值排队，因为您拥有工作线程，否则只有一个线程将退出，其他线程将等待您的进程退出。你可以通过查看第一个项目来改变它，只有当它不是null时才删除它 - 从而将标记留在那里用于所有线程。所以Consume会改为：
void Consume()
{
while (true) // Keep consuming until
{ // told otherwise.
string item;
lock (locker)
{
while (_itemQ.Count == 0) Monitor.Wait(locker);
item = _itemQ.Peek();
if (item != null) _itemQ.Dequeue();
else Monitor.PulseAll(); // if the head of the queue is null then make sure all other threads are also woken up so they can quit
}
if (item == null) // This signals our exit.
{
if (Interlocked.Decrement(ref _ActiveThreads) == 0)
{
OnCompleted(EventArgs.Empty);
}
return;
}
DoSomething(item); // Execute item.
OnItemProcessed();
}
}
答案 1 :(得分：2)
在PCQueue类中，您需要跟踪有多少工作线程仍处于活动状态，并且只有在指示所有线程结束后才会引发TaskCompleted。
void Consume()
{
while (true)
{
string item;
lock (locker)
{
while (_itemQ.Count == 0) Monitor.Wait(locker);
item = _itemQ.Dequeue();
}
if (item == null)
{
// activeThreads is set to the number of workers in the constructor.
if (Interlocked.Decrement(ref activeThreads) == 0)
{
// Take a snapshot of the event so that a null check + invocation is safe.
// This works because delegates are immutable.
var copy = TaskCompleted;
if (copy != null)
{
copy(this, new EventArgs());
}
}
return;
}
DoSomething(item); // Execute item.
}
}
其他几点：
TaskCompleted事件处理程序封送回UI线程。PercentCompleted引发DoSomething，但没有明确指出队列假设保留该值的项数将没有意义。关于这一点，我第二次Chris' recommendation。