class Program
{
// 使用BeginXXX/EndXXX和IAsyncResult对象的方式被称为异步编程模型（APM模式）
delegate string RunOnThreadPool(out int threadId);
static void Main(string[] args)
{
int threadId = 0;
// 给委托变量赋值
RunOnThreadPool poolDelegate = Test;
var t = new Thread(() => { Test(out threadId); });
t.Start();
t.Join();
Console.WriteLine($"1.返回的线程Id：{threadId}");
// 通过调用委托变量的BeginInvoke方法来运行委托（执行Test方法）
IAsyncResult ar = poolDelegate.BeginInvoke(out threadId, Callback, "异步委托调用");
ar.AsyncWaitHandle.WaitOne();
// 调用委托的EndInvoke会等待异步操作（Test方法）完成
// 异步操作执行完成之后，开始执行回掉函数；异步操作和回掉函数很可能会被线程池中同一个工作线程执行
string result = poolDelegate.EndInvoke(out threadId, ar);
Console.WriteLine($"2.返回的线程Id：{threadId}");
Console.WriteLine($"返回值：{result}");
Console.ReadKey();
}
static void Callback(IAsyncResult ar)
{
Console.WriteLine("开始执行回掉函数...");
Console.WriteLine($"异步状态：{ar.AsyncState}");
Console.WriteLine($"是否为线程池中的线程：{Thread.CurrentThread.IsThreadPoolThread}");
Console.WriteLine($"线程池工作线程Id：{Thread.CurrentThread.ManagedThreadId}");
}
static string Test(out int threadId)
{
Console.WriteLine("开始测试方法...");
Console.WriteLine($"是否为线程池中的线程：{Thread.CurrentThread.IsThreadPoolThread}");
Thread.Sleep(TimeSpan.FromSeconds(2));
threadId = Thread.CurrentThread.ManagedThreadId;
return $"线程Id：{threadId}";
}
}
向线程池中放入异步操作
class Program
{
static void Main(string[] args)
{
ThreadPool.QueueUserWorkItem(AsyncOperation);
Thread.Sleep(TimeSpan.FromSeconds(2));
ThreadPool.QueueUserWorkItem(AsyncOperation, "async state");
Thread.Sleep(TimeSpan.FromSeconds(2));
ThreadPool.QueueUserWorkItem(state =>
{
Console.WriteLine($"操作状态：{state}");
Console.WriteLine($"工作线程Id：{Thread.CurrentThread.ManagedThreadId}");
Thread.Sleep(TimeSpan.FromSeconds(2));
}, "lambda state");
const int x = 1;
const int y = 2;
const string lambdaState = "lambda state 2";
// 使用闭包机制，无需传递lambda表达式的状态参数
ThreadPool.QueueUserWorkItem(_ =>
{
Console.WriteLine($"操作状态：{x + y},{lambdaState}");
Console.WriteLine($"工作线程Id：{Thread.CurrentThread.ManagedThreadId}");
Thread.Sleep(TimeSpan.FromSeconds(2));
});
Console.ReadKey();
}
static void AsyncOperation(object state)
{
Console.WriteLine($"操作状态：{state ?? "(null)"}");
Console.WriteLine($"工作线程Id：{Thread.CurrentThread.ManagedThreadId}");
Thread.Sleep(TimeSpan.FromSeconds(2));
}
}
线程池与并行度：
static void Main(string[] args)
{
int threadCount = 500;
var sw = new Stopwatch();
sw.Start();
UseThreads(threadCount);
sw.Stop();
Console.WriteLine($"手动创建线程执行操作耗时：{sw.ElapsedMilliseconds}");
sw.Reset();
sw.Start();
UseThreadPool(threadCount);
sw.Stop();
Console.WriteLine($"使用线程池执行操作耗时：{sw.ElapsedMilliseconds}");
Console.ReadKey();
}
static void UseThreads(int threadCount)
{
using (CountdownEvent cdEvt = new CountdownEvent(threadCount))
{
Console.WriteLine("开始创建线程");
for (int i = 0; i < threadCount; i++)
{
var thread = new Thread(() =>
{
Console.WriteLine($"是否为线程池中的线程：{Thread.CurrentThread.IsThreadPoolThread}，线程Id：{Thread.CurrentThread.ManagedThreadId}");
Thread.Sleep(TimeSpan.FromSeconds(0.1));
cdEvt.Signal();
});
thread.Start();
}
cdEvt.Wait();
Console.WriteLine();
}
}
/// <summary>
/// 线程池的用途是执行时间短的操作，使用线程池可以减少并行度消耗及节省操作系统资源
/// </summary>
/// <param name="threadCount"></param>
static void UseThreadPool(int threadCount)
{
using (CountdownEvent cdEvt = new CountdownEvent(threadCount))
{
Console.WriteLine("开始使用线程池");
for (int i = 0; i < threadCount; i++)
{
ThreadPool.QueueUserWorkItem(_ =>
{
Console.WriteLine($"是否为线程池中的线程：{Thread.CurrentThread.IsThreadPoolThread}，线程Id：{Thread.CurrentThread.ManagedThreadId}");
Thread.Sleep(TimeSpan.FromSeconds(0.1));
cdEvt.Signal();
});
}
cdEvt.Wait();
Console.WriteLine();
}
}
//在收到信号特定次数后取消阻止等待线程的同步基元
//可以使用取消令牌取消等待操作
//创建实例后，可以递增信号计数
//在 Reset 方法调用返回 Wait 后，可以重用实例
public void Test()
{
IEnumerable<Data> source = GetData();
using (CountdownEvent e = new CountdownEvent(1))
{
foreach (Data element in source)
{
e.AddCount();
ThreadPool.QueueUserWorkItem(delegate (object state)
{
try
{
ProcessData(state);
}
finally
{
e.Signal();
}
},
element);
}
}
}
static IEnumerable<Data> GetData()
{
return new List<Data>() { new Data(1), new Data(2), new Data(3), new Data(4), new Data(5) };
}
static void ProcessData(object obj)
{
DataWithToken dataWithToken = (DataWithToken)obj;
if (dataWithToken.Token.IsCancellationRequested)
{
Console.WriteLine("Canceled before starting {0}", dataWithToken.Data.Num);
return;
}
for (int i = 0; i < 10000; i++)
{
if (dataWithToken.Token.IsCancellationRequested)
{
Console.WriteLine("Cancelling while executing {0}", dataWithToken.Data.Num);
return;
}
Thread.SpinWait(100000);
}
Console.WriteLine("Processed {0}", dataWithToken.Data.Num);
}
static void EventWithCancel()
{
IEnumerable<Data> source = GetData();
CancellationTokenSource cts = new CancellationTokenSource();
Task.Factory.StartNew(() =>
{
if (Console.ReadKey().KeyChar == 'c') cts.Cancel();
});
CountdownEvent e = new CountdownEvent(1);
foreach (Data element in source)
{
DataWithToken item = new DataWithToken(element, cts.Token);
e.AddCount();
ThreadPool.QueueUserWorkItem(delegate (object state)
{
ProcessData(state);
if (!cts.Token.IsCancellationRequested)
e.Signal();
},
item);
}
e.Signal();
try
{
e.Wait(cts.Token);
}
catch (OperationCanceledException oce)
{
if (oce.CancellationToken == cts.Token)
{
Console.WriteLine("User canceled.");
}
else
{
throw; //We don't know who canceled us!
}
}
finally
{
e.Dispose();
cts.Dispose();
}
}
}
class Data
{
public int Num { get; set; }
public Data(int i) { Num = i; }
public Data() { }
}
class DataWithToken
{
public CancellationToken Token { get; set; }
public Data Data { get; private set; }
public DataWithToken(Data data, CancellationToken ct)
{
this.Data = data;
this.Token = ct;
}
}
取消异步操作：
static void Main(string[] args)
{
using (var cts = new CancellationTokenSource())
{
CancellationToken token = cts.Token;
ThreadPool.QueueUserWorkItem(_ =>
{
AsyncOperation1(token);
});
Thread.Sleep(TimeSpan.FromSeconds(2));
cts.Cancel();
}
using (var cts = new CancellationTokenSource())
{
CancellationToken token = cts.Token;
ThreadPool.QueueUserWorkItem(_ =>
{
AsyncOperation2(token);
});
Thread.Sleep(TimeSpan.FromSeconds(2));
cts.Cancel();
}
using (var cts = new CancellationTokenSource())
{
CancellationToken token = cts.Token;
ThreadPool.QueueUserWorkItem(_ =>
{
AsyncOperation3(token);
});
Thread.Sleep(TimeSpan.FromSeconds(2));
cts.Cancel();
}
Console.ReadKey();
}
static void AsyncOperation1(CancellationToken token)
{
Console.WriteLine("启动第一个异步操作");
for (int i = 0; i < 5; i++)
{
// 轮询检查IsCancellationRequested属性
if (token.IsCancellationRequested)
{
Console.WriteLine("第一个异步操作被取消啦~~~");
return;
}
Thread.Sleep(TimeSpan.FromSeconds(1));
}
Console.WriteLine("第一个异步操作完成");
}
static void AsyncOperation2(CancellationToken token)
{
try
{
Console.WriteLine("启动第二个异步操作");
for (int i = 0; i < 5; i++)
{
// 抛出异常，取消操作时，通过操作之外的代码来处理
token.ThrowIfCancellationRequested();
Thread.Sleep(TimeSpan.FromSeconds(1));
}
Console.WriteLine("第二个异步操作完成");
}
catch (OperationCanceledException ex)
{
Console.WriteLine($"第二个异步操作被取消，异常消息：{ex.Message}");
}
}
static void AsyncOperation3(CancellationToken token)
{
bool cancellationFlag = false;
// 注册回调函数，当操作被取消时，线程池将调用该回调函数
token.Register(() => { cancellationFlag = true; });
Console.WriteLine("启动第三个异步操作");
for (int i = 0; i < 5; i++)
{
if (cancellationFlag)
{
Console.WriteLine("第三个异步操作被取消啦~~~");
return;
}
Thread.Sleep(TimeSpan.FromSeconds(1));
}
Console.WriteLine("第三个异步操作完成");
}
在线程池中使用等待事件处理器及超时
static void Main(string[] args)
{
RunOperation(TimeSpan.FromSeconds(5));
RunOperation(TimeSpan.FromSeconds(7));
Console.ReadKey();
}
static void RunOperation(TimeSpan workerOperationTs)
{
using (var evt = new ManualResetEvent(false))
using (var cts = new CancellationTokenSource())
{
Console.WriteLine("注册操作超时的方法...");
var worker = ThreadPool.RegisterWaitForSingleObject(evt,
(state, isTimeout) => WorkerOperationWait(cts, isTimeout),
null, workerOperationTs, true);
Console.WriteLine("开始长时间操作...");
ThreadPool.QueueUserWorkItem(_ =>
{
WorkerOperation(cts.Token, evt);
});
Thread.Sleep(workerOperationTs.Add(TimeSpan.FromSeconds(2)));
worker.Unregister(evt);
}
}
static void WorkerOperation(CancellationToken token, ManualResetEvent evt)
{
for (int i = 0; i < 6; i++)
{
if(token.IsCancellationRequested)
{
Console.WriteLine("异步操作被取消");
return;
}
Thread.Sleep(TimeSpan.FromSeconds(1));
}
evt.Set();
}
static void WorkerOperationWait(CancellationTokenSource cts,bool isTimeout)
{
if(isTimeout)
{
cts.Cancel();
Console.WriteLine("异步操作超时并被取消了");
}
else
{
Console.WriteLine("异步操作完成");
}
}
