All Questions
Tagged with .net-4.5 async-await
248
questions
377
votes
3
answers
443k
views
Do you have to put Task.Run in a method to make it async?
I'm trying to understand async await in the simplest form. I want to create a very simple method that adds two numbers for the sake of this example, granted, it's no processing time at all, it's just ...
- 9,539
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
212
votes
4
answers
163k
views
Using 'async' in a console application in C# [duplicate]
I have this simple code:
public static async Task<int> SumTwoOperationsAsync()
{
var firstTask = GetOperationOneAsync();
var secondTask = GetOperationTwoAsync();
return await ...
- 147k
209
votes
11
answers
111k
views
Is it possible to await an event instead of another async method?
In my C#/XAML metro app, there's a button which kicks off a long-running process. So, as recommended, I'm using async/await to make sure the UI thread doesn't get blocked:
private async void ...
- 9,577
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
190
votes
4
answers
225k
views
How to cancel a Task in await?
I'm playing with these Windows 8 WinRT tasks, and I'm trying to cancel a task using the method below, and it works to some point. The CancelNotification method DOES get called, which makes you think ...
- 25.8k
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
132
votes
3
answers
48k
views
Is async HttpClient from .Net 4.5 a bad choice for intensive load applications?
I recently created a simple application for testing the HTTP call throughput that can be generated in an asynchronous manner vs a classical multithreaded approach.
The application is a able to ...
- 8,212
112
votes
2
answers
113k
views
HttpClient.GetAsync with network credentials
I'm currently using HttpWebRequest to get a website. I'd like to use the await pattern, which is not given for HttpWebRequests. I found the class HttpClient, which seems to be the new Http worker ...
- 2,582
87
votes
13
answers
137k
views
How to 'await' raising an EventHandler event
Sometimes the event pattern is used to raise events in MVVM applications by or a child viewmodel to send a message to its parent viewmodel in a loosely coupled way like this.
Parent ViewModel
...
- 143k
85
votes
4
answers
39k
views
What's the difference between InvokeAsync and BeginInvoke for WPF Dispatcher
I noticed in .NET 4.5 that the WPF Dispatcher had gotten a new set of methods to execute stuff on the Dispatcher's thread called InvokeAsync. Before, .NET 4.5 we had Invoke and BeginInvoke which ...
- 35.5k
79
votes
1
answer
148k
views
Await operator can only be used within an Async method [duplicate]
I'm trying to make a simple program to test the new .NET async functionality within Visual Studio 2012. I generally use BackgroundWorkers to run time-consuming code asynchronously, but sometimes it ...
- 2,108
61
votes
4
answers
34k
views
What are the differences between using ConfigureAwait(false) and Task.Run?
I understand that it's recommended to use ConfigureAwait(false) for awaits in library code so that subsequent code does not run in the caller's execution context, which could be a UI thread. I also ...
- 41.5k
57
votes
10
answers
56k
views
awaitable Task based queue
I'm wondering if there exists an implementation/wrapper for ConcurrentQueue, similar to BlockingCollection where taking from the collection does not block, but is instead asynchronous and will cause ...
- 119k
51
votes
6
answers
30k
views
NetworkStream.ReadAsync with a cancellation token never cancels
Here the proof.
Any idea what is wrong in this code ?
[TestMethod]
public void TestTest()
{
var tcp = new TcpClient() { ReceiveTimeout = 5000, SendTimeout = 20000 };
tcp....
- 12.4k
51
votes
7
answers
18k
views
Awaiting Asynchronous function inside FormClosing Event
I'm having a problem where I cannot await an asynchronous function inside of the FormClosing event which will determine whether the form close should continue. I have created a simple example that ...
- 838
50
votes
6
answers
32k
views
Task.Yield - real usages?
I've been reading about Task.Yield , And as a Javascript developer I can tell that's it's job is exactly the same as setTimeout(function (){...},0); in terms of letting the main single thread deal ...
- 147k
45
votes
3
answers
28k
views
Brief explanation of Async/Await in .Net 4.5
How does Asynchronous tasks (Async/Await) work in .Net 4.5?
Some sample code:
private async Task<bool> TestFunction()
{
var x = await DoesSomethingExists();
var y = await ...
- 8,824
41
votes
3
answers
30k
views
Creating an async method in .NET 4.0 that can be used with "await" in .NET 4.5
I have a .NET project that uses C# in .NET 4.0 and VS2010.
What I would like to do is add some async overloads to my library to make doing async programming easier for users in .NET 4.5 with the ...
- 48.7k
39
votes
1
answer
14k
views
HttpClient.PostAsync knocks out the app with exit code 0
Everything was working today until it stopped... Below is the minimum source code (I'm using VS 2012 Update 1, .Net 4.5). When I run it, app exits upon calling client.PostAsync() and so it never ...
- 992
39
votes
7
answers
18k
views
OperationContext.Current is null after first await when using async/await in WCF service
I am using async/await pattern in .NET 4.5 to implement some service methods in WCF.
Example service:
Contract:
[ServiceContract(Namespace = "http://async.test/")]
public interface IAsyncTest
{
...
- 1,770
36
votes
3
answers
40k
views
Using Async Await keywords with Dapper
I want to use a micro-orm and decided to go with Dapper.
But can't seem to find any mentions of it supporting the new async/await syntax. Async queries are important for me.
Can someone provide a ...
- 12.7k
35
votes
2
answers
68k
views
How to determine a 404 response status when using the HttpClient.GetAsync()
I am trying to determine the response returned by HttpClient's GetAsync method in the case of 404 errors using C# and .NET 4.5.
At present I can only tell that an error has occurred rather than the ...
- 4,381
33
votes
2
answers
10k
views
Custom awaitables for dummies
In Async/Await FAQ, Stephen Toub says:
An awaitable is any type that exposes a GetAwaiter method which returns a valid awaiter.
...
An awaiter is any type returned from an awaitable’s ...
- 7,185
30
votes
3
answers
16k
views
How to use await on methods in interfaces
When implementing against an interface (because of mocking, remoting or similiar) using the await keyword and having an interface with methods returning Task<> :
interface IFoo
{
Task<...
- 900
28
votes
2
answers
22k
views
awaiting on an observable
So in the sad days of C# 4.0, I created the following "WorkflowExecutor" class that allowed asynchronous workflows in the GUI thread by hacking into IEnumerable's "yield return" continuations to wait ...
- 10.7k
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
25
votes
3
answers
15k
views
async/await and opening a FileStream?
I came across the following question when trying to determine if I was using the Stream methods such as ReadAsync and CopyToAsync correctly:
C# 4.5 file read performance sync vs async
In this ...
- 9,492
25
votes
2
answers
33k
views
How can I await an async method without an async modifier in this parent method?
I have a method that I want to await but I don't want to cause a domino effect thinking anything can call this calling method and await it. For example, I have this method:
public bool Save(string ...
- 9,539
24
votes
2
answers
7k
views
HttpContext.Current.Items after an Async operation
Consider the following ASP.NET Web API Delegating Handler:
public class MyHandler : DelegatingHandler
{
protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage ...
- 2,593
24
votes
3
answers
26k
views
Task status changes to RanToCompletion if the Task await's something
The question describes the same problem found here - MSDN Developer Forum. The question does not have an accepted answer, neither any of the answers given can be applied to my case (hence a different ...
- 13.3k
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
22
votes
4
answers
19k
views
Why is await async so slow?
I finally got VS2012 and got a simple demo up and working to check out the potential performance boost of async and await, but to my dismay it is slower! Its possible I'm doing something wrong, but ...
- 4,209
22
votes
2
answers
32k
views
Using async / await with DataReader ? ( without middle buffers!)
My goal is simple , I want to do Asynchronous I/O calls (using async await) - but :
Without using DataFlow dependency ( like in this answer)
Without middle buffers( not like this answer)
The ...
- 147k
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
20
votes
3
answers
6k
views
How to attach CancellationTokenSource to DownloadStringTaskAsync method and cancel the async call?
I an creating a sample example to call link using WebClient using async and await method now I want to attach cancel async call functionality also. But I am not able to get CancellationTokenSource ...
- 3,441
19
votes
3
answers
4k
views
Is LogicalOperationStack incompatible with async in .Net 4.5
Trace.CorrelationManager.LogicalOperationStack enables having nested logical operation identifiers where the most common case is logging (NDC). Should it still work with async-await?
Here's a simple ...
- 115k
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
17
votes
2
answers
7k
views
What difference does it make - running an 'async' action delegate with a Task.Run (vs default action delegate)?
I am trying to get my head around async/await and thought I did understand few things about the usage. But still not quite clear what would be the actual benefit in a scenario like below.
Look at the ...
- 2,692
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
3
answers
9k
views
MVC4 + async/await + return response before action completes
In my MVC4 app I need to add a controller for uploading and processing large files. Immediately after the file is uploaded I need to start async processing of that file and return response to the ...
- 1,475
16
votes
2
answers
12k
views
How do I kick off an entity stored procedure in EF6 async and not wait for a return?
I'd like to just punt a call over to the SQL Server and not wait for a return. I have an imported Entity Function from a Stored Procedure that I'd like to call asynchronously this way in Entity ...
- 978
16
votes
3
answers
14k
views
C# have async function call synchronous function or synchronous function call async function
I'm writing a C# .Net 4.5 library for doing common sql database operations (backup, restore, execute script, etc.). I want to have both synchronous and asynchronous functions for each operation, as ...
- 23.4k
15
votes
1
answer
33k
views
The 'await' operator can only be used with an async lambda expression [duplicate]
I'm trying to copy a list of files to a directory. I'm using async / await.
But I've been getting this compilation error
The 'await' operator can only be used within an async lambda
expression. ...
- 5,625
15
votes
1
answer
10k
views
Why do I have to use await for a method to run asynchronously. What if I don't want to wait for the method to finish before continuing? [duplicate]
I've been pouring through MSDN docs all day, and their philosophy of asynchronous coding is confusing me. As I understand it, the thread that calls the async method will not be blocked if the async ...
- 429
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
15
votes
2
answers
9k
views
Does Task.Delay start a new thread?
The following code should (at least in my opinion) create 100 Tasks, which are all waiting in parallel (that's the point about concurrency, right :D ?) and finish almost at the same time. I guess for ...
- 2,199
15
votes
4
answers
2k
views
Code Contracts + Async in .NET 4.5: "The method or operation is not implemented"
I receive the following compilation error from ccrewrite when using Code Contracts 1.4.51019.0 in VS2012 on Windows 7 x64: "The method or operation is not implemented."
It appears to be caused by a ...
- 6,521
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