A value type that wraps a Task
Documentation of ValueTask<TResult> struct.
More reading: Understanding the Whys, Whats, and Whens of ValueTask.
Questions tagged [valuetask]
35 questions
41
votes
5 answers
Task.WhenAll for ValueTask
Is there an equivalent of Task.WhenAll accepting ValueTask?
I can work around it using
Task.WhenAll(tasks.Select(t => t.AsTask()))
This will be fine if they're all wrapping a Task but it will force the useless allocation of a Task object for real…
Stefano d'Antonio
- 5,874
- 3
- 32
- 45
29
votes
2 answers
What is the ValueTask equivalent of Task.CompletedTask?
I am implementing IAsyncDisposable which requires me to return a ValueTask, but sometimes my dispose method has nothing to do. How should I return in this case?
At the moment I'm returning new ValueTask(Task.CompletedTask) which seems to work but…
Andy
- 10,412
- 13
- 70
- 95
12
votes
1 answer
Should I await ValueTask?
Which would be a valid implementation of ValueTask please?
Cache service returns data either from cache or DB.
public async ValueTask> GetEmployeesFacts()
{
try
{
var facts =…
sziszu
- 490
- 1
- 6
- 16
7
votes
2 answers
Should I return ValueTask if I still use TaskCompletionSource to implement asynchrony?
Is there still a benefit in returning ValueTask if I use TaskCompletionSource to implement actual asynchrony?
As I understand it, the purpose of ValueTask is to reduce allocations, but allocations are still there when awaiting…
avo
- 10,101
- 13
- 53
- 81
7
votes
2 answers
The ValueTask and the async state machine
According to the documentation a ValueTask...
Provides a value type that wraps a Task and a TResult, only one of which is used.
My question is about the state machine that the C# compiler generates when the async keyword is…
Theodor Zoulias
- 34,835
- 7
- 69
- 104
5
votes
1 answer
Why is Task faster than ValueTask?
I'm doing a benchmark on Task and ValueTask. Source code below:
#LINQPad optimize+ // Enable compiler optimizations
void Main()
{
Util.AutoScrollResults = true;
…
Will Huang
- 2,955
- 2
- 37
- 90
5
votes
2 answers
Convert a ValueTask to a non generic ValueTask
The question asked here is the same as the one here and is aimed to create a definitive solution to it.
The most accurate answer is by Stephen Toub himself in this issue that is exactly about this question. The "recommendended code" is the following…
Spi
- 686
- 3
- 18
5
votes
3 answers
Is there any sense to return ValueTask from method that internally awaits some Tasks
I have an async method that looks approximately like this:
async Task ParseStream()
{
var a = await reader.ReadInt32();
var b = await reader.ReadInt32();
return a + b;
}
This method is going to work synchronously most of the time…
wiuwiu
- 63
- 1
- 5
4
votes
2 answers
What is the point of ValueTask.Preserve()?
ValueTask and ValueTask have a Preserve() method which is summarized as "Gets a ValueTask that may be used at any point in the future."
What does that mean and when should we use it? Does it imply that a 'normal' ValueTask can't be used "at…
Petrusion
- 940
- 4
- 11
4
votes
0 answers
EF Core DbSet AddAsync method: Should the async method be used in 100% of the cases?
The documentation on the AddAsync method states that
This method is async only to allow special value generators, such as the one used by 'Microsoft.EntityFrameworkCore.Metadata.SqlServerValueGenerationStrategy.SequenceHiLo', to access the database…
0xDECAFBAD
- 627
- 1
- 8
- 21
4
votes
1 answer
How to choose the return type of an async delegate
I am passing an async delegate to the LINQ Select method, and I would prefer to get a list of ValueTasks instead of a list of Tasks. How can I do it? Example:
var result = (new[] { 0 }).Select(async x => await…
Theodor Zoulias
- 34,835
- 7
- 69
- 104
3
votes
3 answers
Why can an async method with return type ValueTask await a regular Task without generating a compiler error?
The following code does not compile
public ValueTask Foo()
{
return Task.Delay(1000);
}
but yields an Error CS0029: Cannot implicitly convert type 'System.Threading.Tasks.Task' to 'System.Threading.Tasks.ValueTask as expected.
However,…
Joerg
- 790
- 2
- 10
- 23
3
votes
3 answers
Is there a ContinueWith for ValueTask?
If an API returns a ValueTask or ValueTask, is there a way to perform a ContinueWith on it, like I'm able to do with Task? Is there a Microsoft-provided NuGet library for doing so with .NET Standard 2.0?
D.R.
- 20,268
- 21
- 102
- 205
2
votes
2 answers
How to Pause/Resume an asynchronous worker, without incurring memory allocation overhead?
I have an asynchronous method that contains an endless while loop. This loop is paused and resumed frequently by the main thread of the program. For this purpose I am using currently the PauseTokenSource class from the Nito.AsyncEx package:
private…
Theodor Zoulias
- 34,835
- 7
- 69
- 104
2
votes
2 answers
How to return a canceled ValueTask that propagates an OperationCanceledException, without async/await?
I am writting an API that has a ValueTask return type, and accepts a CancellationToken. In case the CancellationToken is already canceled upon invoking the method, I would like to return a canceled ValueTask (IsCanceled == true), that…
Theodor Zoulias
- 34,835
- 7
- 69
- 104