async-await

问题 There are many reasons to put a token in the constructor of a task, mentioned here: Cancellation token in Task constructor: why? With the use of keywords, async / await, how is that working? for example my code below: public async Task MethodAsync(CancellationToken token) { await Method01Async(); await Method02Async(); } Although it is an asynchronous process. In no time I used "Task.StartNext" or "Task.Run" or "new Task". To be able to specify my cancellation token, how can I do? 回答1: You

问题 I am trying to implement a method called ReadAllLinesAsync using the async feature. I have produced the following code: private static async Task<IEnumerable<string>> FileReadAllLinesAsync(string path) { using (var reader = new StreamReader(path)) { while ((await reader.ReadLineAsync()) != null) { } } return null; } private static void Main() { Button buttonLoad = new Button { Text = "Load File" }; buttonLoad.Click += async delegate { await FileReadAllLinesAsync("test.txt"); //100mb file!

问题 I have the following method in an interface.. Task<SearchResult<T>> SearchAsync(TU searchOptions); works great. Now i'm trying to make a unit test to test when something goes wrong - and the code throws an exception. In this case, I've setup my method to throw an HttpRequestException . My unit test fails to say that I threw that exception .. var result = Should.Throw<HttpRequestException> (async () => await service.SearchAsync(searchOptions)); the error message from the unit test is Shouldly

问题 I'm looking for best practice around calling multiple async methods where each next method relies on the values returned from one before. I'm experimenting with 2 approaches 1) https://dotnetfiddle.net/waPL9L public async void Main() { var T1 = await Sum(2,5); var T2 = await Sum(T1, 7); var T3 = await Sum(T2, 7); Console.WriteLine(T3); } public async Task<int> Sum(int num1, int num2){ return await Task.Run(() => { // for some reason if i use Sleep... I don't see any results at all... //Thread

问题 AFAIK - ( and I read a lot about it), asynchronous methods ( not asynchronous delegates !) exists to solve the "thread is blocked" problem when dealing with I/O operations like : reading a file or downloading a file : Richter shows it quite clearly here : Task<T> is not related to the i/o blocking issue. it is simply just like open a thread ( plus extra efficiency + functionality ) - but it still causes a thread to consume cpu quanta etc. And here is my question : I've read (msdn) that : An

问题 I was trying to find an IO bottleneck in my class and surprisingly noticed that sw.Write("m"); sw.Flush() can be 20000 faster then await sw.WriteAsync("m"); Await sw.FlushAsync(); when writing 1000000 messages to a file. Does, by any chance, anyone know why? My bet is StreamWriter 's constructor taking a String does not parametrize a stream for async usage. The code below can be launched from C# interactive. Yes, it's not the best place to measure the speed but it will show the matter at hand

问题 I am trying to write a multi threading search and then display all the results once the tasks have finished running but currently I don't understand how to process the results once all the tasks are complete My code is as follows: private async void DoSearchAsync() { var productResults = await SearchProductsAsync(CoreCache.AllProducts); var brochureResults = await SearchBrochuresAsync(CoreCache.AllBrochures); _searchResults.AddRange(productResults); _searchResults.AddRange(brochureResults);

问题 I am in the process of writing my first Koa.js app, and having recently been introduced to the ES2016 (aka ES7) features of async / await , I wanted to make use of these. I found that my Google skills were not up to the task, and the few snippets of code I could find were either for the standard Koa (using generators) or otherwise not-as-bleeding-edge-as-ES7. See my answer below for how I got my tests running. 回答1: I'm still a beginner, so it's likely that a lot of this can be optimised

问题 How to tell if the continuation initiated by TaskCompletionSource.TrySetResult is going to be executed synchronously or asynchronously? For example: // class A void RegisterNotification(TaskCompletionSource<object> tcs) { this.source.NotificationEvent += (s, eData) => { Debug.WriteLine("A.before"); tcs.TrySetResult(eData.Result); Debug.WriteLine("A.after"); DoProcessingA(); }; } // class B async Task RequestNotificationAsync() { var tcs = new TaskCompletionSource<object>(); this.a

问题 I need to send an email as a result of a SignalR hub invocation. I don't want the send to execute synchronously, as I don't want to tie up WebSocket connections, but I would like the caller to be informed, if possible, if there were any errors. I thought I'd be able to use something like this in the hub (minus error handling and all other things that I want it to do): public class MyHub : Hub { public async Task DoSomething() { var client = new SmtpClient(); var message = new MailMessage(/*