All Questions
Tagged with .net-4.5 task-parallel-library
108
questions
221
votes
6
answers
98k
views
What's the difference between Task.Start/Wait and Async/Await?
I may be missing something but what is the difference between doing:
public void MyMethod()
{
Task t = Task.Factory.StartNew(DoSomethingThatTakesTime);
t.Wait();
UpdateLabelToSayItsComplete();
}...
- 39.5k
190
votes
5
answers
119k
views
Async/await vs BackgroundWorker
In the past few days I have tested the new features of .net 4.5 and c# 5.
I like its new async/await features. Earlier I had used BackgroundWorker to handle longer processes in the background with ...
- 3,999
149
votes
6
answers
199k
views
Run two async tasks in parallel and collect results in .NET 4.5
I've been trying for a while to get something I thought would be simple working with .NET 4.5
I want to fire off two long running tasks at same time and collect the
results in in the best C# 4.5 (...
- 143k
103
votes
3
answers
83k
views
Proper way to implement a never ending task. (Timers vs Task)
So, my app needs to perform an action almost continuously (with a pause of 10 seconds or so between each run) for as long as the app is running or a cancellation is requested. The work it needs to do ...
- 2,103
28
votes
1
answer
26k
views
Passing a task as parameter
I am not sure whether this is possible, so here me out:
I have a sequence of action to perform multiple
async Task MethodA(...)
{
// some code
// a call to specific Async IO bound method
...
- 6,398
27
votes
2
answers
6k
views
Task.WhenAny and Unobserved Exceptions
Let's say I have three tasks, a, b, and c. All three are guaranteed to throw an exception at a random time between 1 and 5 seconds. I then write the following code:
await Task.WhenAny(a, b, c);
This ...
- 39.4k
23
votes
3
answers
1k
views
When to use the "await" keyword
I'm writing a web page, and it calls some web services. The calls looked like this:
var Data1 = await WebService1.Call();
var Data2 = await WebService2.Call();
var Data3 = await WebService3.Call();
...
- 4,417
20
votes
4
answers
19k
views
Task.WaitAll not waiting for task to complete
While trying to figure out the new (maybe not so new now, but new to me, anyway) Task asynchronous programming in C#, I ran into a problem that took me a bit to figure out, and I'm not sure why.
I ...
- 357
17
votes
3
answers
14k
views
Why does Task.Delay() allow an infinite delay?
After my application froze I tracked down the cause to a thread waiting on a task created by Task.Delay() (or TaskEx.Delay() in .NET 4.0) for which it provided a computed TimeSpan that, due to a bug, ...
- 16k
16
votes
3
answers
7k
views
.NET 4 equivalent of Task.WhenAll()
In .NET 4, is there any functional equivalent to .NET 4.5's System.Threading.Tasks.Task.WhenAll()?
The goal is to wrap up multiple async tasks into a single one that is completed when all of its ...
- 26.4k
16
votes
1
answer
585
views
.Net 4.5 killed my TPL, now what?
Exhibit 1: some code wrapping an Async (not async!) network call into a Task
public static Task<byte[]> GetAsync(IConnection connection, uint id)
{
ReadDataJob jobRDO = new ReadDataJob();
...
- 65.2k
15
votes
1
answer
10k
views
.Net 4.5 Svcutil generates two operations with the same name (Method and MethodAsync)
I am consuming a predefined wsdl with svcutil a la:
svcutil some_service.wsdl
one of the methods generated has the following signature:
[System.ServiceModel.OperationContractAttribute(Action="http:/...
- 11.8k
14
votes
3
answers
12k
views
Where does an async Task throw Exception if it is not awaited?
I have the following example: (please also read comments in code, as it will make more sense )
public async Task<Task<Result>> MyAsyncMethod()
{
Task<Result> resultTask = ...
- 33k
13
votes
2
answers
338
views
Task.Run in Static Initializer
Consider the following code.
static class X
{
public static int Value = Task.Run(() => 0).Result;
}
class Program
{
static void Main(string[] args)
{
var value = X.Value;
}...
- 77.2k
11
votes
2
answers
5k
views
Can a Task have multiple awaiters?
I am toying around with an async service for a Windows 8 project and there are some async calls of this service, which should only be called once at a time.
public async Task CallThisOnlyOnce()
{
...
user604613
11
votes
1
answer
4k
views
Async CTP - Recommended approach for task scheduling
I'm currently working on a largely asynchronous application which uses TAP throughout. Every class which has methods for spawning Tasks also has a TaskScheduler injected into it. This allows us to ...
- 6,521
10
votes
1
answer
5k
views
Exception handling in fire and forget for C# 5 (in .net 4.5)
Consider the following "fire-and-forget" use case:
A caller requests some data from my method. My method checks the cache to see if the data is already there. If it's not, it fetches it from the ...
- 1,188
10
votes
2
answers
2k
views
Task not garbage collected
In the following program, I'd expect the task to get GC'd, but it doesn't. I've used a memory profiler which showed that the CancellationTokenSource holds a reference to it even though the task is ...
- 22.6k
9
votes
1
answer
3k
views
Customizing ActionBlock<T>
I want to implement a prioritised ActionBlock<T>. So that i can Conditionally give priority to some TInput items by using a Predicate<T>.
I read Parallel Extensions Extras Samples and ...
- 2,193
8
votes
2
answers
1k
views
What is the purpose of passing CancellationToken to Task.Factory.StartNew()
In the following code a CancellationToken is passed to the .StartNew(,) method as the 2nd parameter, but is only usable by the Action via the closure in the lambda. So, what is the purpose of passing ...
- 11.4k
8
votes
4
answers
2k
views
Why does the localInit Func get called multiple times per thread in Parallel.ForEach
I was writing some code to process a lot of data, and I thought it would be useful to have Parallel.ForEach create a file for each thread it creates so the output doesn't need to be synchronized (by ...
- 1,558
7
votes
3
answers
6k
views
async/await. Where is continuation of awaitable part of method performed?
I am really curious how async/await enables your program not to be halted.
I really like the way how Stephen Cleary explains async/await: "I like to think of "await" as an "asynchronous wait". That is ...
- 37.3k
7
votes
5
answers
726
views
Unwrapping IObservable<Task<T>> into IObservable<T> with order preservation
Is there a way to unwrap the IObservable<Task<T>> into IObservable<T> keeping the same order of events, like this?
Tasks: ----a-------b--c----------d------e---f---->
Values: ----...
- 2,350
7
votes
3
answers
4k
views
Task.Factory.ContinueWhenAny continue when any task finish without exception
I have 3 tasks in my application that are responsible for getting data from databases.
Till now I had all tasks executed one after one. If first finished and had Result then this was my data, if now I ...
- 4,857
7
votes
1
answer
413
views
What other silent changes did happen from .Net Frameworkf v.4.0 to 4.5? [closed]
We want to switch to .net 4.5 cause it offers many improvements.
But...sometimes I found some tricky details about not trivial changes in the framework.
Lets look for TPL unobserved exception ...
- 13.7k
7
votes
2
answers
2k
views
Multi-Threading a Large C# Application Using async/await
All, I have been given the job to multi-thread a large C# application. To do this I have chosen to go use async/await. I am well aware of the use of IProgress<T> to report progress to the UI (...
- 23.5k
6
votes
1
answer
4k
views
Task Parallel Library Code Freezes in a Windows Forms Application - Works fine as a Windows Console Application
This question is a follow-up to a previous question that I had asked:
How to Perform Multiple "Pings" in Parallel using C#
I was able to get the accepted answer (a Windows console ...
- 3,412
6
votes
2
answers
2k
views
What in the Rx Framework allows me to return an IObservable<T> while awaiting other methods during creation?
I've been working on creating an IObservable<T> implementation using the Reactive Extensions for Twitter's streaming APIs.
From a high level an HTTP request is sent and the connection is kept ...
- 74.1k
6
votes
2
answers
2k
views
Is TPL DataFlow included with either .NET 4.5 or .NET 4.5.1?
I'm confused. We upgraded our project recently to .NET 4.5.1. We installed .NET 4.5.1 on our servers.
I'm referencing assembly System.Threading.Tasks.Dataflow from the GAC at C:\windows\Microsoft....
- 21.4k
6
votes
2
answers
5k
views
How to implement continuously running dataflow blocks in TPL?
I have producer/consumer dataflow block set-up using BufferBlock and ActionBlock and it is working fine inside Console application;
After adding all items into BurfferBlock and Linking BufferBlock ...
- 311
5
votes
2
answers
5k
views
Is it possible to cancel a C# Task without a CancellationToken?
I'm need to cancel an API call that returns a Task, but it doesn't take a CancellationToken as a parameter, and I can't add one.
How can I cancel that Task?
In this particular case, I'm using ...
- 151
5
votes
4
answers
6k
views
List of objects with async Task methods, execute all concurrently
Given the following:
BlockingCollection<MyObject> collection;
public class MyObject
{
public async Task<ReturnObject> DoWork()
{
(...)
return await ...
- 76.7k
5
votes
1
answer
2k
views
Task continuations always run even when specifying TaskContinuationOptions
I want to run some code when an async task completes successfully.
From reading documentation and examples on the web, I thought I could use Task.ContinueWith and specify TaskContinuationOptions....
- 5,890
5
votes
1
answer
4k
views
Is CancellationTokenSource.CancelAfter() leaky?
The release of the Async Targeting Pack prompted me to use ILSpy to have a look at what Task-based Asynchronous Pattern (TAP) extension methods were provided there (some of which I have already ...
- 16k
4
votes
4
answers
4k
views
What is the best way to return completed Task?
What is the best way to return a completed Task object?
It is possible to write Task.Delay(0), or Task.FromResult<bool>(true) whatever.
But what is the most efficient way?
- 1,140
4
votes
4
answers
2k
views
Create reusable processing logic on top of predefined blocks with TPL dataflow?
I love TPL dataflow.
Well, an interesting design choice is that, most predefined block use Delegates to allow us to implement processing logic. That looks good in simple scenarios. But let's think ...
- 530
4
votes
1
answer
2k
views
Cold Tasks and TaskExtensions.Unwrap
I've got a caching class that uses cold (unstarted) tasks to avoid running the expensive thing multiple times.
public class AsyncConcurrentDictionary<TKey, TValue> : System.Collections....
- 5,038
4
votes
2
answers
6k
views
return Task.ContinueWith<TResult>() without knowing TResult
How do I create and return a continuation Task using reflection or by any other means if I only have access the Task?
I need a way to let an exception in the continuation travel back to the original ...
- 267
4
votes
1
answer
731
views
Async CTP - Ambient CancellationToken and IProgress
Bearing in mind the Async CTP promotes implicit scheduling via an ambient SynchronizationContext, is there any reason why I should not make my CancellationToken and IProgress ambient too?
I'm ...
- 6,521
4
votes
1
answer
82
views
How do I make non-essential computations run in the background?
This question is in follow up to Why is this code running synchronously? . I realize that my real question is at a higher level than the one in that post. The question I now ask, below, is "how do I ...
- 2,093
4
votes
0
answers
830
views
CallContext - What are the recommendations for using this going forwards? [closed]
Does anyone know if there's any planned support in upcoming versions of .NET for storing objects in the ambient execution context? There's a definite need for it, as highlighted in the following pages:...
- 6,521
3
votes
2
answers
3k
views
Writing to a file from multiple threads without lock
I need to write data buffer by buffer in to a file from different threads. To avoid locking I am writing into different files, say 'file_1','file_2' and at last merges all these files to 'file'. Is ...
- 115
3
votes
3
answers
2k
views
async Methods correct? Resharper warning
in my Method RecalcChartAsync i do some time intensive stuff.. so i thought i'll do some things async.
I want to start the two Methods CreateHistogramAsync CalculatePropValuesAsync and in the ...
- 2,053
3
votes
4
answers
1k
views
Correct usage of Async/Await for Multiple Tasks To Db
I have a simple scenario but I would like to know if my approach is correct, is it better advised to chose a single task to save my failed orders or can i kick off and fire off multiple tasks and wait ...
- 4,334
3
votes
1
answer
5k
views
Best way to make send bulk emails parallel
I am new to TPL (Task Parallel Library) and I'm having a hard time trying to configure my process to run tasks in parallel.
I'm working on an application to send bulk emails (like thousands per minute,...
- 844
3
votes
2
answers
1k
views
How to use async/await with a library that uses an event-based asynchronous pattern?
I use a library that has an asynchronous method called DoWork(...) that will raise a WorkDone event when the operation completes.
I would like to write a method that calls this library, but instead ...
- 19.5k
3
votes
2
answers
3k
views
TaskEx.Yield(TaskScheduler)
Last month I asked the following question which resulted in my learning of TaskEx.Yield:
Can async methods have expensive code before the first 'await'?
However, I have since realized that ...
- 6,521
3
votes
5
answers
2k
views
Howto: Parallel.Foreach executes many processes, after each process run a new process (but one at a time)? [closed]
I'm sure someone knows this and I will be very thankful for the answer. I don't know much about delegates and asynch and the like - so please give me a general example of how I could implement.
I ...
- 1,215
3
votes
1
answer
142
views
The Mysterious "usage" Tag in Visual Studio Documentation XML Comment Tags
I often use XML documentation to document my classes, methods and properties but take a look at this method from Microsoft:
Usage? What kind of sorcery is this? How does one emulate this wizardry?
...
- 2,101
3
votes
3
answers
2k
views
In parallel call, limit executions per second
Using TPL / Parallel.ForEach is there an out-of-the-box way to limit the number of times a method is called per unit of time (i.e. no more than 50 calls per second). This is different than limiting ...
- 36.3k