It’s somewhat weird to read but yes, the exception will bubble up to the calling code – but only if you await or Wait() the call to Foo. public async Task Foo() { var x = await DoSomethingAsync(); } public async void DoFoo() { try { await Foo(); } catch (ProtocolException ex) { // The … Read more
Actually, async/await is not that magical. The full topic is quite broad but for a quick yet complete enough answer to your question I think we can manage. Let’s tackle a simple button click event in a Windows Forms application: public async void button1_Click(object sender, EventArgs e) { Console.WriteLine(“before awaiting”); await GetSomethingAsync(); Console.WriteLine(“after awaiting”); } … Read more
Both answers didn’t mention the awaitable Task.WhenAll: var task1 = DoWorkAsync(); var task2 = DoMoreWorkAsync(); await Task.WhenAll(task1, task2); The main difference between Task.WaitAll and Task.WhenAll is that the former will block (similar to using Wait on a single task) while the latter will not and can be awaited, yielding control back to the caller until … Read more
After you use WhenAll, you can pull the results out individually with await: var catTask = FeedCat(); var houseTask = SellHouse(); var carTask = BuyCar(); await Task.WhenAll(catTask, houseTask, carTask); var cat = await catTask; var house = await houseTask; var car = await carTask; You can also use Task.Result (since you know by this point … Read more
You are misusing the API. Here’s the situation: in ASP.NET, only one thread can handle a request at a time. You can do some parallel processing if necessary (borrowing additional threads from the thread pool), but only one thread would have the request context (the additional threads do not have the request context). This is … Read more
You can specify a MaxDegreeOfParallelism in a ParallelOptions parameter: Parallel.ForEach( listOfWebpages, new ParallelOptions { MaxDegreeOfParallelism = 4 }, webpage => { Download(webpage); } ); MSDN: Parallel.ForEach MSDN: ParallelOptions.MaxDegreeOfParallelism
Note the guidelines for performing work on a UI thread, collected on my blog: Don’t block the UI thread for more than 50ms at a time. You can schedule ~100 continuations on the UI thread per second; 1000 is too much. There are two techniques you should use: 1) Use ConfigureAwait(false) when you can. E.g., … Read more
Your misunderstanding is extremely common. Many people are taught that multithreading and asynchrony are the same thing, but they are not. An analogy usually helps. You are cooking in a restaurant. An order comes in for eggs and toast. Synchronous: you cook the eggs, then you cook the toast. Asynchronous, single threaded: you start the … Read more
Look at the WAITFOR command. E.g. — wait for 1 minute WAITFOR DELAY ’00:01′ — wait for 1 second WAITFOR DELAY ’00:00:01′ This command allows you a high degree of precision but is only accurate within 10ms – 16ms on a typical machine as it relies on GetTickCount. So, for example, the call WAITFOR DELAY … Read more
No, it is blocking. Have a look at the specification of the algorithm. However a maybe easier to understand implementation is given on MDN: if (!Array.prototype.forEach) { Array.prototype.forEach = function(fun /*, thisp */) { “use strict”; if (this === void 0 || this === null) throw new TypeError(); var t = Object(this); var len = … Read more