task-parallel-library – Page 14

Regarding usage of Task.Start() , Task.Run() and Task.Factory.StartNew()

October 25, 2022 by Tarik

Task.Run is a shorthand for Task.Factory.StartNew with specific safe arguments: Task.Factory.StartNew( action, CancellationToken.None, TaskCreationOptions.DenyChildAttach, TaskScheduler.Default); It was added in .Net 4.5 to help with the increasingly frequent usage of async and offloading work to the ThreadPool. Task.Factory.StartNew (added with TPL in .Net 4.0) is much more robust. You should only use it if Task.Run isn’t … Read more

How to cancel a Task in await?

October 23, 2022 by Tarik

Read up on Cancellation (which was introduced in .NET 4.0 and is largely unchanged since then) and the Task-Based Asynchronous Pattern, which provides guidelines on how to use CancellationToken with async methods. To summarize, you pass a CancellationToken into each method that supports cancellation, and that method must check it periodically. private async Task TryTask() … Read more

Async/await vs BackgroundWorker

October 20, 2022 by Tarik

This is likely TL;DR for many, but, I think comparing await with BackgroundWorker is like comparing apples and oranges and my thoughts on this follow: BackgroundWorker is meant to model a single task that you’d want to perform in the background, on a thread pool thread. async/await is a syntax for asynchronously awaiting on asynchronous … Read more

When to dispose CancellationTokenSource?

October 16, 2022 by Tarik

Speaking about whether it’s really necessary to call Dispose on CancellationTokenSource… I had a memory leak in my project and it turned out that CancellationTokenSource was the problem. My project has a service, that is constantly reading database and fires off different tasks, and I was passing linked cancellation tokens to my workers, so even … Read more

No ConcurrentList in .Net 4.0?

October 13, 2022 by Tarik

I gave it a try a while back (also: on GitHub). My implementation had some problems, which I won’t get into here. Let me tell you, more importantly, what I learned. Firstly, there’s no way you’re going to get a full implementation of IList<T> that is lockless and thread-safe. In particular, random insertions and removals … Read more

What’s the difference between Task.Start/Wait and Async/Await?

October 12, 2022 by Tarik

I may be missing something You are. what is the difference between doing Task.Wait and await task? You order your lunch from the waiter at the restaurant. A moment after giving your order, a friend walks in and sits down next to you and starts a conversation. Now you have two choices. You can ignore … Read more

Create a completed Task

October 11, 2022 by Tarik

The newest version of .Net (v4.6) is adding just that, a built-in Task.CompletedTask: Task completedTask = Task.CompletedTask; That property is implemented as a no-lock singleton so you would almost always be using the same completed task.

Cancellation token in Task constructor: why?

October 10, 2022 by Tarik

Passing a CancellationToken into the Task constructor associates it with the task. Quoting Stephen Toub’s answer from MSDN: This has two primary benefits: If the token has cancellation requested prior to the Task starting to execute, the Task won’t execute. Rather than transitioning to Running, it’ll immediately transition to Canceled. This avoids the costs of … Read more

What is the use for Task.FromResult in C#

October 9, 2022 by Tarik

There are two common use cases I’ve found: When you’re implementing an interface that allows asynchronous callers, but your implementation is synchronous. When you’re stubbing/mocking asynchronous code for testing.

HttpClient – A task was cancelled?

October 8, 2022 by Tarik

There’s 2 likely reasons that a TaskCanceledException would be thrown: Something called Cancel() on the CancellationTokenSource associated with the cancellation token before the task completed. The request timed out, i.e. didn’t complete within the timespan you specified on HttpClient.Timeout. My guess is it was a timeout. (If it was an explicit cancellation, you probably would … Read more