You can definitely do this in the latest versions of async for .NET, using .NET 4.5 Beta. The previous post from ‘usr’ points to a good article written by Stephen Toub, but the less announced news is that the async semaphore actually made it into the Beta release of .NET 4.5 If you look at … Read more
Take a look at this example, Stephen has a clear answer for you: So this is what happens, starting with the top-level method (Button1_Click for UI / MyController.Get for ASP.NET): The top-level method calls GetJsonAsync (within the UI/ASP.NET context). GetJsonAsync starts the REST request by calling HttpClient.GetStringAsync (still within the context). GetStringAsync returns an uncompleted … Read more
Wait and await – while similar conceptually – are actually completely different. Wait will synchronously block until the task completes. So the current thread is literally blocked waiting for the task to complete. As a general rule, you should use “async all the way down”; that is, don’t block on async code. On my blog, … Read more
There is one sneaky case when return in normal method and return await in async method behave differently: when combined with using (or, more generally, any return await in a try block). Consider these two versions of a method: Task<SomeResult> DoSomethingAsync() { using (var foo = new Foo()) { return foo.DoAnotherThingAsync(); } } async Task<SomeResult> … Read more
You’re effectively using promises inside the promise constructor executor function, so this the Promise constructor anti-pattern. Your code is a good example of the main risk: not propagating all errors safely. Read why there. In addition, the use of async/await can make the same traps even more surprising. Compare: let p = new Promise(resolve => … Read more
Asynchronous programming does “grow” through the code base. It has been compared to a zombie virus. The best solution is to allow it to grow, but sometimes that’s not possible. I have written a few types in my Nito.AsyncEx library for dealing with a partially-asynchronous code base. There’s no solution that works in every situation, … Read more
In case you are familiar with Task<T> or Promise<T> and the async/ await pattern, then you can skip right to the “How to use a Future with the widgets in Flutter” section. What is a Future and how do I use it? Well, the documentation says: An object representing a delayed computation. That is correct. … Read more
When using async and await the compiler generates a state machine in the background. Here’s an example on which I hope I can explain some of the high-level details that are going on: public async Task MyMethodAsync() { Task<int> longRunningTask = LongRunningOperationAsync(); // independent work which doesn’t need the result of LongRunningOperationAsync can be done … Read more
The reason for async-await is, that whenever your thread has to wait for some other process to finish, your thread can look around to see if it can do something useful instead of waiting idly. This is especially useful for communication oriented tasks: query data from a database, fetching information from the internet, writing data … Read more
The best practice for async/await is to use async “all the way down” (unless you really and truly don’t care about Method1 waiting for Method2 to complete). It’s possible to mix Task.Wait (or similar constructs) with async code, but it’s a bad idea because it can lead to deadlocks. The best thing here would be, … Read more