private async void button1_Click(object sender, EventArgs e)
{
await BackupFile();
}
public async Task BackupFile()
{
await Task.Run(() =>
{
for (var i = 0; i < partCount; i++)
{
upload(FilePart);//how to creat a new task at here
//i don't want to wait here, i want to upload all part at same time
}
//wait here.
//if total part got 10, then how to wait 10 task complete
//after 10 task complete
Console.WriteLine("Upload Successful");
});
}
How to create a new task in loop and how to wait all task complete to
execute next line code
You should try task combinator WhenAll:
public async Task BackupFileAsync()
{
var uploadTasks = new List<Task>();
for (var i = 0; i < partCount; i++)
{
var uploadTask = Task.Run(() => upload(FilePart));
uploadTasks.Add(uploadTask)
}
await Task.WhenAll(uploadTasks);
Console.WriteLine("Upload Successful");
}
Related
I've an existing code I wrote some time ago, that works but I dislike the fact that the thread I start remains in loop.
This piece of code is a consumer on an IBMMQ code, waiting for messages to be processed.The problem I've is that with the following code
private Task ExecuteQueuePolling(CancellationToken cancellationToken)
{
return Task.Factory.StartNew(() =>
{
ConnectToAccessQueue();
Logger.Debug($"Accessed to the queue {queueName}");
Logger.DebugFormat("Repeating timer started, checking frequency: {checkingFrequency}",
checkingFrequency);
while (!cancellationToken.IsCancellationRequested)
{
Logger.Trace( () => "Listening on queues for new messages");
// isChecking = true;
var mqMsg = new MQMessage();
var mqGetMsgOpts = new MQGetMessageOptions
{ WaitInterval = (int)checkingFrequency.TotalMilliseconds };
// 15 second limit for waiting
mqGetMsgOpts.Options |= MQC.MQGMO_WAIT | MQC.MQGMO_FAIL_IF_QUIESCING |
MQC.MQCNO_RECONNECT_Q_MGR | MQC.MQOO_INPUT_AS_Q_DEF;
try
{
mqQueue.Get(mqMsg, mqGetMsgOpts);
if (string.Compare(mqMsg.Format, MQC.MQFMT_STRING, StringComparison.Ordinal) == 0)
{
var text = mqMsg.ReadString(mqMsg.MessageLength);
Logger.Debug($"Message received : [{text}]");
Message message = new Message { Content = text };
foreach (var observer in observers)
observer.OnNext(message);
}
else
{
Logger.Warn("Non-text message");
}
}
catch (MQException ex)
{
if (ex.Message == MQC.MQRC_NO_MSG_AVAILABLE.ToString())
{
Logger.Trace("No messages available");
//nothing to do, emtpy queue
}
else if (ex.Message == MQC.MQRC_CONNECTION_BROKEN.ToString())
{
Logger.ErrorException("MQ Exception, trying to recconect", ex);
throw new ReconnectException();
}
}
Thread.Sleep(100);
}
},cancellationToken);
}
//Calling method
try
{
string queueManagerName = configuration.GetValue<string>("IBMMQ:QUEUE_MANAGER_NAME");
// var queueManager = new MQQueueManager(queueManagerName,dictionary2);
QueueMonitor monitor = new QueueMonitor(configuration, "IMPORTER_RECEIVER_TEST");
//_subscription = monitor.Subscribe(receiver);
await monitor.StartAsync(cts.Token).ConfigureAwait(false);
}
catch (Exception e)
{
log.Error(e, "Error creating the queue monitor or it's subscription");
}
finally
{
WaitForCancel(cts);
}
The call to await monitor.StartAsync(cts.Token).ConfigureAwait(false); remains pending.
How should I modify my code, so that the call returns and in background the task continue to loop?
Thanks in advance
Here is how you can simplify your code by replacing Thread.Sleep with Task.Delay:
private async Task ExecuteQueuePolling(CancellationToken cancellationToken)
{
while (true)
{
// Process mqQueue here
await Task.Delay(100, cancellationToken);
}
}
Task.Delay has the advantage that accepts a CancellationToken, so in case of cancellation the loop will exit immediately. This could be important if the pooling of the MQ was lazier (for example every 5 seconds).
private static Task _runningTask;
static void Main(string[] args)
{
var cts = new CancellationTokenSource();
_runningTask = ExecuteQueuePolling(cts.Token);
WaitForCancel(cts);
}
private static void WaitForCancel(CancellationTokenSource cts)
{
var spinner = new SpinWait();
while (!cts.IsCancellationRequested
&& _runningTask.Status == TaskStatus.Running) spinner.SpinOnce();
}
private static Task ExecuteQueuePolling(CancellationToken cancellationToken)
{
var t = new Task(() =>
{
while (!cancellationToken.IsCancellationRequested)
; // your code
if (cancellationToken.IsCancellationRequested)
throw new OperationCanceledException();
}, cancellationToken, TaskCreationOptions.LongRunning);
t.Start();
return t;
}
I've got the following code which seems to run fine apart from the continuation on the WhenAll ... await Task.WhenAll(syncTasks).ContinueWith ... is run before all four methods are completed. Would appreciate any guidance on what I'm doing wrong here. I don't really feel like I understand how to arrange complex async functionality and what seems to be happening supports that. This is in a Xamarin App BTW although I don't suppose that really matters.
private async Task SyncItems()
{
var updateItemOnes = Task.Run(() =>
{
UpdateItemOnesToServer(itemOnesToUpdate).ContinueWith(async (result) => {
if (!result.IsFaulted && !result.IsCanceled)
{
await UpdateItemOnesToLocal(itemOnesToUpdate);
}
});
});
syncTasks.Add(updateItemOnes);
var updateItemTwos = Task.Run(() =>
{
UpdateItemTwosToServer(itemTwosToUpdate).ContinueWith(async (result) => {
if (!result.IsFaulted && !result.IsCanceled)
{
await UpdateItemTwosToLocal(itemTwosToUpdate);
}
});
});
syncTasks.Add(updateItemTwos );
//Show Loading Dialog
await Task.WhenAll(syncTasks).ContinueWith((result) => {
if (!result.IsFaulted && !result.IsCanceled)
{
//Success
}
else
{
//Error
}
//Hide Loading Dialog
});
}
private async Task UpdateItemOnesToServer(IEnumerable<Item> itemOnesToUpdate)
{
try
{
var listofTasks = new List<Task>();
foreach (var item in itemOnesToUpdate)
{
var convertItemOneTask = Task.Run(async () => {
//Convert Image File in Item to Base64 here
});
listofTasks.Add(convertItemOneTask);
}
await Task.WhenAll(listofTasks);
var response = await _apiManager.SaveItemOnes(itemOnesToUpdate);
if (response.IsSuccessStatusCode)
{
//Update ItemOnes for Local Update with Response Values
}
}
catch
{
throw;
}
}
private async Task UpdateItemOnesToLocal(IEnumerable<Item> itemOnesToUpdate)
{
var listOfTasks = new List<Task<bool>>();
foreach (var itemOne in itemOnesToUpdate)
{
listOfTasks.Add(_localService.UpdateItemOne(itemOne));
}
await Task.WhenAll<bool>(listOfTasks);
}
private async Task UpdateItemTwosToServer(IEnumerable<ItemOne> itemTwosToUpdate)
{
try
{
var listofTasks = new List<Task>();
foreach (var item in itemTwosToUpdate)
{
var convertItemTwoTask = Task.Run(async () => {
//Convert Image File in Item to Base64 here
});
listofTasks.Add(convertItemTwoTask);
}
await Task.WhenAll(listofTasks);
var response = await _apiManager.SaveItemTwos(itemTwosToUpdate);
if (response.IsSuccessStatusCode)
{
//Update ItemTwos for Local Update with Response Values
}
}
catch
{
throw;
}
}
private async Task UpdateItemTwosToLocal(IEnumerable<ItemTwo> itemTwosToUpdate)
{
var listOfTasks = new List<Task<bool>>();
foreach (var itemTwo in itemTwosToUpdate)
{
listOfTasks.Add(_localService.UpdateItemTwo(itemTwo));
}
await Task.WhenAll<bool>(listOfTasks);
}
Thanks in advance to anyone who can provide a little clarity. It will be much appreciated.
So there are a few problems with this code.
someTask.ContinueWith(X)
Basically this says "once the someTask is completed, do X" (there's more going on but in this case think of it like this). However if you await someTask this will not include the ContinueWith part. So like this the Task.WhenAll(syncTasks) will not wait on your ContinueWith parts.
var updateItemOnes = Task.Run(() => UpdateItemOnesToServer()) wrappers. There is no awaiting here, so this will create a Task that just starts the UpdateItemOnesToServer task. That is done instantly.
If you would like to see what is happening in practice use this test class:
class TestAsyncClass
{
public async Task Run()
{
var tasks = new List<Task>();
Console.WriteLine("starting tasks");
var task1 = Task.Run(() => {
FakeServerCall1().ContinueWith(async (result) =>
{
if (!result.IsFaulted && !result.IsCanceled)
await FakeLocalCall1();
});
});
tasks.Add(task1);
var task2 = Task.Run(() => {
FakeServerCall2().ContinueWith(async (result) =>
{
if (result.IsCompletedSuccessfully)
await FakeLocalCall2();
});
});
tasks.Add(task2);
Console.WriteLine("starting tasks completed");
await Task.WhenAll(tasks);
Console.WriteLine("tasks completed");
}
public async Task<bool> FakeServerCall1()
{
Console.WriteLine("Server1 started");
await Task.Delay(3000);
Console.WriteLine("Server1 completed");
return true;
}
public async Task<bool> FakeServerCall2()
{
Console.WriteLine("Server2 started");
await Task.Delay(2000);
Console.WriteLine("Server2 completed");
return true;
}
public async Task<bool> FakeLocalCall1()
{
Console.WriteLine("Local1 started");
await Task.Delay(1500);
Console.WriteLine("Local1 completed");
return true;
}
public async Task<bool> FakeLocalCall2()
{
Console.WriteLine("Local2 started");
await Task.Delay(2000);
Console.WriteLine("Local2 completed");
return true;
}
}
You'll see that the output is as follows:
starting tasks
starting tasks completed
Server1 started
Server2 started
tasks completed
Server2 completed
Local2 started
Server1 completed
Local1 started
Local2 completed
Local1 completed
Notice here the "tasks completed" is called straight after starting the two tasks.
Now if we change the Run method like this I think we'll get the functionality you're looking for:
public async Task Run()
{
var tasks = new List<Task>();
Console.WriteLine("starting tasks");
var task1 = Task.Run(async () =>
{
await FakeServerCall1();
await FakeLocalCall1();
});
tasks.Add(task1);
var task2 = Task.Run(async() =>
{
await FakeServerCall2();
await FakeLocalCall2();
});
tasks.Add(task2);
Console.WriteLine("starting tasks completed");
await Task.WhenAll(tasks);
Console.WriteLine("tasks completed");
}
Which will output:
starting tasks
starting tasks completed
Server1 started
Server2 started
Server2 completed
Local2 started
Server1 completed
Local1 started
Local2 completed
Local1 completed
tasks completed
So we see here that Local1 is always after Server1 and Local2 is always after Server2 and "tasks completed" is always after Local1 & Local2
Hope this helps!
Edit:
From you comment you said you would like to see any exceptions that occurred in the process. This is where you could use ContinueWith (it is also fired when exceptions are throw:
await Task.WhenAll(tasks).ContinueWith((result) =>
{
if (result.IsFaulted)
{
foreach (var e in result.Exception.InnerExceptions)
{
Console.WriteLine(e);
}
}
});
If you change the following test calls:
public async Task<bool> FakeServerCall2()
{
Console.WriteLine("Server2 started");
await Task.Delay(1000);
Console.WriteLine("Crashing Server2");
throw new Exception("Oops server 2 crashed");
}
public async Task<bool> FakeLocalCall1()
{
Console.WriteLine("Local1 started");
await Task.Delay(1500);
Console.WriteLine("crashing local1");
throw new Exception("Oh ohh, local1 crashed");
}
This will be your output:
starting tasks
starting tasks completed
Server1 started
Server2 started
Crashing Server2
Server1 completed
Local1 started
crashing local1
System.Exception: Oh ohh, local1 crashed
at TestConsoleApp.TestAsyncClass.FakeLocalCall1() in ~\TestConsoleApp\TestConsoleApp\Program.cs:line 67
at TestConsoleApp.TestAsyncClass.b__0_0() in ~\TestConsoleApp\TestConsoleApp\Program.cs:line 17
System.Exception: Oops server 2 crashed
at TestConsoleApp.TestAsyncClass.FakeServerCall2() in ~\TestConsoleApp\TestConsoleApp\Program.cs:line 59
at TestConsoleApp.TestAsyncClass.b__0_1() in ~\TestConsoleApp\TestConsoleApp\Program.cs:line 23
tasks completed
I have a async function and used the Progress< int>
to progress long process After I run another task, it seems that the many progress reports are running.
private async void Listbox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var progress = new Progress<int>(percent =>
{
prg.Value = percent;
});
isCanceled = true;
await ExecuteManuallyCancellableTaskAsync(progress);
}
and this is my func
public async Task ExecuteManuallyCancellableTaskAsync(IProgress<int> progress)
{
var mprogress = 0;
prg.Value = 0;
using (var cancellationTokenSource = new CancellationTokenSource())
{
cancellationTokenSource.Cancel();
var SearchTask = Task.Run(async () =>
{
foreach (var file in await GetFileListAsync(GlobalData.Config.DataPath))
{
if (isCanceled)
{
cancellationTokenSource.Cancel();
return;
}
mprogress += 1;
progress.Report((mprogress * 100 / TotalItem));
await Dispatcher.InvokeAsync(() =>
{
// my codes
}, DispatcherPriority.Background);
}
});
await SearchTask;
}
}
and this is result that you can see different value in progressbar same time.
In short you are not using the CancellationTokenSource correctly for 2 reasons; firstly it needs to be passed around to any async methods that you are calling in order to truly cancel them, secondly it will likely need to live for longer than just inside the scope where you are using it.
Try something like this (complete with comments to hopefully make it easy to follow):
private CancellationTokenSource cancellationTokenSource; // And remove isCanceled as this is causing some of the issues
private async void Listbox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var progress = new Progress<int>(percent =>
{
prg.Value = percent;
});
// Make sure any current processing is stopped.
cancellationTokenSource?.Cancel();
// Prepare to be able to cancel the next round of processing.
cancellationTokenSource = new CancellationTokenSource();
await ExecuteManuallyCancellableTaskAsync(progress, cancellationTokenSource.Token);
}
public async Task ExecuteManuallyCancellableTaskAsync(IProgress<int> progress, CancellationToken cancelToken)
{
var mprogress = 0;
prg.Value = 0;
await Task.Run(async () =>
{
// You will need to implement checks against the CancellationToken in your GetFileListAsync method also.
foreach (var file in await GetFileListAsync(GlobalData.Config.DataPath, cancelToken))
{
mprogress += 1;
progress.Report((mprogress * 100 / TotalItem));
// Only update the UI if we have not been requested to cancel.
if (!cancelToken.IsCancellationRequested)
{
await Dispatcher.InvokeAsync(() =>
{
// my codes
}, DispatcherPriority.Background);
}
}
}, cancelToken); // Pass in the token to allow the Task to be cancelled.
}
I have a method RestartAsync which starts a method DoSomethingAsync. When RestartAsync is called again it should cancel DoSomethingAsyncand await until it is finished (DoSomethingAsync can NOT be cancelled synchronously and it should NOT be called when a previous task is still in progress).
My first approach looked like this:
public async Task RestartTest()
{
Task[] allTasks = { RestartAsync(), RestartAsync(), RestartAsync() } ;
await Task.WhenAll(allTasks);
}
private async Task RestartAsync()
{
_cts.Cancel();
_cts = new CancellationTokenSource();
await _somethingIsRunningTask;
_somethingIsRunningTask = DoSomethingAsync(_cts.Token);
await _somethingIsRunningTask;
}
private static int _numberOfStarts;
private async Task DoSomethingAsync(CancellationToken cancellationToken)
{
_numberOfStarts++;
int numberOfStarts = _numberOfStarts;
try
{
Console.WriteLine(numberOfStarts + " Start to do something...");
await Task.Delay(TimeSpan.FromSeconds(1)); // This operation can not be cancelled.
await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken);
Console.WriteLine(numberOfStarts + " Finished to do something...");
}
catch (OperationCanceledException)
{
Console.WriteLine(numberOfStarts + " Cancelled to do something...");
}
}
The actual output when calling RestartAsync three times looks like this (Note that the second run is cancelling and awaiting the first, but at the same time the third run is also awaiting the first instead of cancelling and awaiting the second one):
1 Start to do something...
1 Cancelled to do something...
2 Start to do something...
3 Start to do something...
2 Finished to do something...
3 Finished to do something...
But what I want to achieve is this output:
1 Start to do something...
1 Cancelled to do something...
2 Start to do something...
2 Cancelled to do something...
3 Start to do something...
3 Finished to do something...
My current solution is the following:
private async Task RestartAsync()
{
if (_isRestarting)
{
return;
}
_cts.Cancel();
_cts = new CancellationTokenSource();
_isRestarting = true;
await _somethingIsRunningTask;
_isRestarting = false;
_somethingIsRunningTask = DoSomethingAsync(_cts.Token);
await _somethingIsRunningTask;
}
Then I get this output:
1 Start to do something...
1 Cancelled to do something...
2 Start to do something...
2 Finished to do something...
Now at least DoSomethingAsync is not started while it is still in progress (Note that third run is ignored, which does not really matter, because it should cancel the second run otherwise).
But this solution doesn't feel good and I have to repeat this ugly pattern wherever I want this kind of behavior. Is there any good pattern or framework for this kind of restart mechanic?
I think the problem is inside RestartAsync method. Beware that an async method will immediately return a task if it's going to await something, so second RestartAsync actually return before it swap its task then third RestartAsync comes in and awaiting the task first RestartAsync.
Also if RestartAsync is going to be executed by multiple thread, you may want to wrap _cts and _somethingIsRunningTask into one and swap values with Interlocked.Exchange method to prevent race condition.
Here is my example code, not fully tested:
public class Program
{
static async Task Main(string[] args)
{
RestartTaskDemo restartTaskDemo = new RestartTaskDemo();
Task[] tasks = { restartTaskDemo.RestartAsync( 1000 ), restartTaskDemo.RestartAsync( 1000 ), restartTaskDemo.RestartAsync( 1000 ) };
await Task.WhenAll( tasks );
Console.ReadLine();
}
}
public class RestartTaskDemo
{
private int Counter = 0;
private TaskEntry PreviousTask = new TaskEntry( Task.CompletedTask, new CancellationTokenSource() );
public async Task RestartAsync( int delay )
{
TaskCompletionSource<bool> taskCompletionSource = new TaskCompletionSource<bool>();
CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();
TaskEntry previousTaskEntry = Interlocked.Exchange( ref PreviousTask, new TaskEntry( taskCompletionSource.Task, cancellationTokenSource ) );
previousTaskEntry.CancellationTokenSource.Cancel();
await previousTaskEntry.Task.ContinueWith( Continue );
async Task Continue( Task previousTask )
{
try
{
await DoworkAsync( delay, cancellationTokenSource.Token );
taskCompletionSource.TrySetResult( true );
}
catch( TaskCanceledException )
{
taskCompletionSource.TrySetCanceled();
}
}
}
private async Task DoworkAsync( int delay, CancellationToken cancellationToken )
{
int count = Interlocked.Increment( ref Counter );
Console.WriteLine( $"Task {count} started." );
try
{
await Task.Delay( delay, cancellationToken );
Console.WriteLine( $"Task {count} finished." );
}
catch( TaskCanceledException )
{
Console.WriteLine( $"Task {count} cancelled." );
throw;
}
}
private class TaskEntry
{
public Task Task { get; }
public CancellationTokenSource CancellationTokenSource { get; }
public TaskEntry( Task task, CancellationTokenSource cancellationTokenSource )
{
Task = task;
CancellationTokenSource = cancellationTokenSource;
}
}
}
This is a concurrency problem. So, you'll need a solution for concurrency problems: a semaphore.
In the generic case, you should account also for when the method being runs throws an OperationCanceledException:
private async Task DoSomethingAsync(CancellationToken cancellationToken)
{
_numberOfStarts++;
int numberOfStarts = _numberOfStarts;
try
{
Console.WriteLine(numberOfStarts + " Start to do something...");
await Task.Delay(TimeSpan.FromSeconds(1)); // This operation can not be cancelled.
await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken);
Console.WriteLine(numberOfStarts + " Finished to do something...");
}
catch (OperationCanceledException)
{
Console.WriteLine(numberOfStarts + " Cancelled to do something...");
throw;
}
}
Try this:
private SemaphoreSlim semaphore = new SemaphoreSlim(1);
private (CancellationTokenSource cts, Task task)? state;
private async Task RestartAsync()
{
Task task = null;
await this.semaphore.WaitAsync();
try
{
if (this.state.HasValue)
{
this.state.Value.cts.Cancel();
this.state.Value.cts.Dispose();
try
{
await this.state.Value.task;
}
catch (OperationCanceledException)
{
}
this.state = null;
}
var cts = new CancellationTokenSource();
task = DoSomethingAsync(cts.Token);
this.state = (cts, task);
}
finally
{
this.semaphore.Release();
}
try
{
await task;
}
catch (OperationCanceledException)
{
}
}
I All,
I have to monitor an async task, which has to be cancellable and do not perform more than specific Time To Live.
I already knew about the following code.
CancellationTokenSource l_cts = new CancellationTokenSource(timemillis);
which will doing the cancellation ( as far i monitor the token in my async method).
However, this NOT gave me any information about WHY he has been cancelled, Timeout or user cancellation? furthermore, the timeout event is delayed while i did not catch the cancellation with
Token.ThrowIfCancellationRequested();
In order to solve these issues, I wrote the timeout process as follow.
static async Task TestAsync(int processDelaySeconds, int cancelDelaySeconds, int timeoutDelaySeconds )
{
CancellationTokenSource l_cts = new CancellationTokenSource();
// the process to monitor
Task l_process = new Task((state) =>
{
Console.WriteLine("Process BEGIN");
// dummy loop
for (int l_i = 0; l_i != processDelaySeconds; l_i++)
{
Thread.Sleep(1000);
l_cts.Token.ThrowIfCancellationRequested();
}
Console.WriteLine("Process END");
}, null, l_cts.Token);
// register timeout
RegisteredWaitHandle l_rwh = ThreadPool.RegisterWaitForSingleObject(l_cts.Token.WaitHandle,
(state, timedOut) =>
{
if (timedOut)
{
l_cts.Cancel();
Console.WriteLine("Timed out");
}
else
{
Console.WriteLine("Cancel Signaled");
}
},
null, (int)TimeSpan.FromSeconds(timeoutDelaySeconds).TotalMilliseconds, true);
// cancel task
if (cancelDelaySeconds > 0)
{
Task l_cancel = new Task(() =>
{
Thread.Sleep(TimeSpan.FromSeconds(cancelDelaySeconds));
l_cts.Cancel();
});
l_cancel.Start();
}
try
{
l_process.Start();
await l_process;
}
catch (OperationCanceledException)
{
Console.WriteLine("Task Cancelled");
}
finally
{
// be sure to unregister the wait handle to cancel the timeout
if (l_process.Status != TaskStatus.Canceled) l_rwh.Unregister(l_cts.Token.WaitHandle);
}
Console.WriteLine("Task Status is : {0}", l_process.Status);
}
static async void Tests()
{
Console.WriteLine("NORMAL PROCESS");
Console.WriteLine("--------------");
await TestAsync(2, 10, 10);
Console.WriteLine();
Console.WriteLine("CANCEL");
Console.WriteLine("------");
await TestAsync(5, 2, 10);
Console.WriteLine();
Console.WriteLine("TIMEOUT");
Console.WriteLine("-------");
await TestAsync(10, 15, 2);
}
Then My question is :
Is there any drawbacks or traps behind the scene ?
A better and more efficient way ??
ps- Goal is performance, not shorter code.
If you need to distinguish between the user's and time-out cancellation, you can use CreateLinkedTokenSource:
using System;
using System.Threading;
using System.Threading.Tasks;
namespace ConsoleApp
{
internal class Program
{
// worker
private static void DoWork(CancellationToken token)
{
for (int i = 0; i < 1000; i++)
{
token.ThrowIfCancellationRequested();
Thread.Sleep(100); // do the work item
}
token.ThrowIfCancellationRequested();
}
// test
private static void Main()
{
var userCt = new CancellationTokenSource();
var combinedCt = CancellationTokenSource.CreateLinkedTokenSource(
userCt.Token);
combinedCt.CancelAfter(3000); // cancel in 3 seconds
Console.CancelKeyPress += (s, e) =>
{
e.Cancel = true;
userCt.Cancel();
};
var task = Task.Run(
() => DoWork(combinedCt.Token),
combinedCt.Token);
try
{
task.Wait();
}
catch (AggregateException ex)
{
Console.WriteLine(ex.InnerException.Message);
if (task.IsCanceled)
{
if (userCt.Token.IsCancellationRequested)
Console.WriteLine("Cancelled by user");
else if (combinedCt.Token.IsCancellationRequested)
Console.WriteLine("Cancelled by time-out");
else
Console.WriteLine("Cancelled by neither user nor time-out");
}
}
}
}
}
As to your original code, you really did not need ThreadPool.RegisterWaitForSingleObject(l_cts.Token.WaitHandle, ...), there's CancellationToken.Register for that, which returns an IDisposable ready for use with using.
In order to know if your Task has been cancelled or timed out, you can use the Task.WaitAny overload which takes a TimeSpan:
// Index will return -1 if timeout has occured, otherwise will print the index of the completed task
var cnclToken = new CancellationTokenSource().Token
var yourTask = Task.Run(() => { /* Do stuff */ }, cnclToken);
var index = Task.WhenAny(new[] { yourTask }, TimeSpan.FromSeconds(1));
http://msdn.microsoft.com/en-us/library/dd235645(v=vs.110).aspx