每次调用Task.Factory.StartNew时，我都会尝试创建一个新线程。问题是如何在不抛出异常的情况下运行代码：
static void Main(string[] args)
{
int firstThreadId = 0;
Task.Factory.StartNew(() => firstThreadId = Thread.CurrentThread.ManagedThreadId);
for (int i = 0; i < 100; i++)
{
Task.Factory.StartNew(() =>
{
while (true)
{
Thread.Sleep(1000);
if (firstThreadId == Thread.CurrentThread.ManagedThreadId)
throw new Exception("The first thread is reused.");
}
});
}
Console.Read();
}
编辑：新代码，如果您对第一个for语句发表评论没有问题。但是，如果你拥有它，WOW，会将“Thread reused”消息写入控制台。你能解释一下，因为我真的很困惑。
static void Main(string[] args)
{
ConcurrentDictionary<int, int> startedThreads = new ConcurrentDictionary<int, int>();
for (int i = 0; i < 10; i++)
{
Task.Factory.StartNew(() =>
{
Task.Factory.StartNew(() =>
{
startedThreads.AddOrUpdate(Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.ManagedThreadId, (a, b) => b);
}, TaskCreationOptions.LongRunning);
for (int j = 0; j < 100; j++)
{
Task.Factory.StartNew(() =>
{
while (true)
{
Thread.Sleep(10);
if (startedThreads.ContainsKey(Thread.CurrentThread.ManagedThreadId))
Console.WriteLine("Thread reused");
}
}, TaskCreationOptions.LongRunning);
}
});
}
Console.Read();
}
答案 0 :(得分：18)
如果在启动任务时指定TaskCreationOptions.LongRunning，则会向调度程序提供提示，默认调度程序将其作为为任务创建新线程的指示符。
这只是一个提示 - 我不确定我是否依赖 ...但我没有看到使用默认调度程序的任何反例。
答案 1 :(得分：4)
添加Jon Skeet的答案，如果你想保证每次都创建一个新线程，你可以编写自己的TaskScheduler来创建一个新线程。
答案 2 :(得分：2)
只需使用新的Thread（）启动线程，然后使用Start（）启动它们
static void Main(string[] args)
{
ConcurrentDictionary<int, int> startedThreads = new ConcurrentDictionary<int, int>();
for (int i = 0; i < 10; i++)
{
new Thread(() =>
{
new Thread(() =>
{
startedThreads.AddOrUpdate(Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.ManagedThreadId, (a, b) => b);
}).Start();
for (int j = 0; j < 100; j++)
{
new Thread(() =>
{
while (true)
{
Thread.Sleep(10);
if (startedThreads.ContainsKey(Thread.CurrentThread.ManagedThreadId))
Console.WriteLine("Thread reused");
}
}).Start();
}
}).Start();
}
Console.Read();
}
任务应该由调度程序管理。 Tasks的整个想法是运行时将决定何时需要新线程。另一方面，如果你确实需要不同的线程，那么代码中的其他内容可能就像Thread.Sleep（）或线程本地存储的过度依赖一样。
正如所指出的，您可以创建自己的TaskScheduler并使用任务来创建线程但是为什么要使用Tasks来开始呢？
答案 3 :(得分：2)
您好，谢谢大家的答案。你们都得到了+1。所有建议的解决方案都不适合我的情况。问题是，当你睡眠一个线程时，它会在某个时间点被重用。上面的人建议：
我不喜欢它，但它有效。基本上我阻止了线程，因此无法重用。贝娄是扩展方法和工作实例。再次，谢谢。
https://gist.github.com/4150635
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
namespace ConsoleApplication
{
public static class ThreadExtensions
{
/// <summary>
/// Blocks the current thread for a period of time so that the thread cannot be reused by the threadpool.
/// </summary>
public static void Block(this Thread thread, int millisecondsTimeout)
{
new WakeSleepClass(millisecondsTimeout).SleepThread();
}
/// <summary>
/// Blocks the current thread so that the thread cannot be reused by the threadpool.
/// </summary>
public static void Block(this Thread thread)
{
new WakeSleepClass().SleepThread();
}
/// <summary>
/// Blocks the current thread for a period of time so that the thread cannot be reused by the threadpool.
/// </summary>
public static void Block(this Thread thread, TimeSpan timeout)
{
new WakeSleepClass(timeout).SleepThread();
}
class WakeSleepClass
{
bool locked = true;
readonly TimerDisposer timerDisposer = new TimerDisposer();
public WakeSleepClass(int sleepTime)
{
var timer = new Timer(WakeThread, timerDisposer, sleepTime, sleepTime);
timerDisposer.InternalTimer = timer;
}
public WakeSleepClass(TimeSpan sleepTime)
{
var timer = new Timer(WakeThread, timerDisposer, sleepTime, sleepTime);
timerDisposer.InternalTimer = timer;
}
public WakeSleepClass()
{
var timer = new Timer(WakeThread, timerDisposer, Timeout.Infinite, Timeout.Infinite);
timerDisposer.InternalTimer = timer;
}
public void SleepThread()
{
while (locked)
lock (timerDisposer) Monitor.Wait(timerDisposer);
locked = true;
}
public void WakeThread(object key)
{
locked = false;
lock (key) Monitor.Pulse(key);
((TimerDisposer)key).InternalTimer.Dispose();
}
class TimerDisposer
{
public Timer InternalTimer { get; set; }
}
}
}
class Program
{
private static readonly Queue<CancellationTokenSource> tokenSourceQueue = new Queue<CancellationTokenSource>();
static void Main(string[] args)
{
CancellationTokenSource tokenSource = new CancellationTokenSource();
tokenSourceQueue.Enqueue(tokenSource);
ConcurrentDictionary<int, int> startedThreads = new ConcurrentDictionary<int, int>();
for (int i = 0; i < 10; i++)
{
Thread.Sleep(1000);
Task.Factory.StartNew(() =>
{
startedThreads.AddOrUpdate(Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.ManagedThreadId, (a, b) => b);
for (int j = 0; j < 50; j++)
Task.Factory.StartNew(() => startedThreads.AddOrUpdate(Thread.CurrentThread.ManagedThreadId, Thread.CurrentThread.ManagedThreadId, (a, b) => b));
for (int j = 0; j < 50; j++)
{
Task.Factory.StartNew(() =>
{
while (!tokenSource.Token.IsCancellationRequested)
{
if (startedThreads.ContainsKey(Thread.CurrentThread.ManagedThreadId)) Console.WriteLine("Thread reused");
Thread.CurrentThread.Block(10);
if (startedThreads.ContainsKey(Thread.CurrentThread.ManagedThreadId)) Console.WriteLine("Thread reused");
}
}, tokenSource.Token, TaskCreationOptions.LongRunning, TaskScheduler.Default)
.ContinueWith(task =>
{
WriteExceptions(task.Exception);
Console.WriteLine("-----------------------------");
}, TaskContinuationOptions.OnlyOnFaulted);
}
Thread.CurrentThread.Block();
}, tokenSource.Token, TaskCreationOptions.LongRunning, TaskScheduler.Default)
.ContinueWith(task =>
{
WriteExceptions(task.Exception);
Console.WriteLine("-----------------------------");
}, TaskContinuationOptions.OnlyOnFaulted);
}
Console.Read();
}
private static void WriteExceptions(Exception ex)
{
Console.WriteLine(ex.Message);
if (ex.InnerException != null)
WriteExceptions(ex.InnerException);
}
}
}
答案 4 :(得分：1)
尝试一下：
var taskCompletionSource = new TaskCompletionSource<bool>();
Thread t = new Thread(() =>
{
try
{
Operation();
taskCompletionSource.TrySetResult(true);
}
catch (Exception e)
{
taskCompletionSource.TrySetException(e);
}
});
void Operation()
{
// Some work in thread
}
t.Start();
await taskCompletionSource.Task;
您还可以编写Action，Func等扩展方法。 例如：
public static Task RunInThread(
this Action action,
Action<Thread> initThreadAction = null)
{
TaskCompletionSource<bool> taskCompletionSource = new TaskCompletionSource<bool>();
Thread thread = new Thread(() =>
{
try
{
action();
taskCompletionSource.TrySetResult(true);
}
catch (Exception e)
{
taskCompletionSource.TrySetException(e);
}
});
initThreadAction?.Invoke(thread);
thread.Start();
return taskCompletionSource.Task;
}
或
public static Task<TResult> RunInThread<T1, T2, TResult>(
this Func<T1, T2, TResult> function,
T1 param1,
T2 param2,
Action<Thread> initThreadAction = null)
{
TaskCompletionSource<TResult> taskCompletionSource = new TaskCompletionSource<TResult>();
Thread thread = new Thread(() =>
{
try
{
TResult result = function(param1, param2);
taskCompletionSource.TrySetResult(result);
}
catch (Exception e)
{
taskCompletionSource.TrySetException(e);
}
});
initThreadAction?.Invoke(thread);
thread.Start();
return taskCompletionSource.Task;
}
并像这样使用它：
var result = await some_function.RunInThread(param1, param2).ConfigureAwait(true);