async-await

问题 I'm reviewing some WPF code of my colleagues, which is a library of UserControl -based components with a lot of async void event and command handlers. These methods currently do not implement any error handling internally. The code in a nutshell: <Window.CommandBindings> <CommandBinding Command="ApplicationCommands.New" Executed="NewCommand_Executed"/> </Window.CommandBindings> private async void NewCommand_Executed(object sender, ExecutedRoutedEventArgs e) { // do some fake async work (and

问题 I am trying following code, it has two parts, one is navigation via prism. When navigation is allowed I am starting a deep load asynchronously but each time with a new context. In later code I would want to cancel pending navigations that are not finished this loading but the below code does not even work so cancellation is a matter for later ;-) navigation logic : no problems here public void OnNavigatedTo(NavigationContext navigationContext) { int relatieId = (int)navigationContext

问题 With the latest version of nodejs 7.6+ I started using async/await. I was using jshint but from what I read they currently do support this syntax and some suggested using eslint. So ok I set eslint up but argh.. it flags async functions too. Parsing error: Unexpected token init (Fatal) I know there is nothing wrong as my code is running fine it's just the linter. Too if I comment out an async function it just flags the next one. IN fact eslint only flags the first async found with this error

问题 I am waiting on multiples task using Task.WhenAll. When one of them generates an exception I would like Task.WhenAll (or any other way of awaiting multiples tasks) to immediately cancel the others tasks and raise an exception. Is it possible? Thanks in advance 回答1: Cancellation is coopertive the WhenAll can't cancel the threads but you can pass all of them a CancellationToken and fire the token when you get a exception. CancellationTokenSource cts = new CancellationTokenSource(); var task1 =

问题 I have a process I would like to run in the background. This is executed with a click of an action link. Action to call: public async Task<ActionResult> ProcessRec() { await Task.Run(() => waitTimer()); return RedirectToAction("Index", "Home"); } public void waitTimer() { Thread.Sleep(10000); } This however waits for the full 10 seconds before redirecting me to my "Index, Home" action. I am very new to Await/Async so I know I am interpreting something wrong here. How do I get the application

问题 I have a very simple service, public class AzureService : IAzureService { private readonly CloudBlobContainer _container; public AzureService(ISettings settings) { var storageAccount = CloudStorageAccount.Parse(settings.BlobConnectionString); var blobClient = storageAccount.CreateCloudBlobClient(); _container = blobClient.GetContainerReference(settings.BlobContainerName); } public Task UploadBlobAsync(string fileName, Stream stream) { var blob = _container.GetBlockBlobReference(fileName);

问题 As we know, C#7 allows to make Main() function asynchronous. What advantages it gives? For what purpose may you use async Main instead of a normal one? 回答1: It's actually C# 7.1 that introduces async main. The purpose of it is for situations where you Main method calls one or more async methods directly. Prior to C# 7.1, you had to introduce a degree of ceremony to that main method, such as having to invoke those async methods via SomeAsyncMethiod().GetAwaiter().GetResult() . By being able to

问题 Does try catch outside of: await Task.Run(() => make sense or just use them only inside of await? private async void Test() { try { await Task.Run(() => { try { DoingSomething(); } catch (Exception ex) { log.Error(ex.Message); } }); } catch (Exception ex) { log.Error(ex.Message); } } 回答1: If you handle Exception inside the delegate (in your case just for logging purpose), await will not raise an exception in normal circumstances. This should be fine. private async Task Test() { await Task.Run

问题 Assume there is a function doRequest(options) , which is supposed to perform an HTTP request and uses http.request() for that. If doRequest() is called in a loop, I want that the next request is made after the previous finished (serial execution, one after another). In order to not mess with callbacks and Promises, I want to use the async/await pattern (transpiled with Babel.js to run with Node 6+). However, it is unclear to me, how to wait for the response object for further processing and

问题 I thought async/await was supported in node 7.4, however this example does not work: const Promise = require('bluebird'); async function main(){ await Promise.delay(1000) } main(); Results in: async function main(){ ^^^^^^^^ SyntaxError: Unexpected token function How can I use async/await with node 7.4? 回答1: Yes async-await is supported in Node.js v7 but its locked behind the harmony flag. Features which are not yet production ready are behind this flag. To use async-await in Node.js v7