Jon Skeet recently asked me how I might go about implementing the following “asynchronous ForEach” behavior: Given what we now know about SemaphoreSlim from my previous post, here’s one way to achieve this: public static Task ForEachAsync<TSource, TResult>(     this IEnumerable<TSource> ...

The C# and Visual Basic compilers implement support for async/await by generating code that utilizes some specific types in the underlying framework.  These types include the “awaiters” used to await things (like Tasks) as well as the “builders” used in handling the lifetime of an async method’s invocation. With t...

Thanks to everyone who attended my "The Zen of Async" presentation on Thursday at the MVP Summit.  As I've had several requests, here are the slides and code for the talk. Toub_MVPSummit2012_ZenOfAsync.zip

At //BUILD/ in September, we blogged about the wealth of new support available for parallelism in the .NET Framework 4.5 Developer Preview.  Since then, we’ve been hard at work on the .NET 4.5 Beta.  With the beta just released, here are a few interesting and related things that are new or have changed since the Developer Preview re...

In my last past, we looked at building an AsyncLock in terms of an AsyncSemaphore.  In this post, we’ll build a more advanced construct, an asynchronous reader/writer lock.An asynchronous reader/writer lock is more complicated than any of the previous coordination primitives we’ve created.  It also involves more policy, meanin...

Last time, we looked at building an AsyncSemaphore.  Here, we’ll look at building support for an async mutual exclusion mechanism that supports scoping via ‘using’. As mentioned in the previous post, semaphores are great for throttling and resource management.  You can give a semaphore an initial count of the number of things to protect, and then ...

In my last few posts, I covered building an AsyncManualResetEvent, an AsyncAutoResetEvent, an AsyncCountdownEvent, and an AsyncBarrier.  In this post, I’ll cover building an AsyncSemaphore class.Semaphores have a wide range of applicability.  They’re great for throttling, for protected access to a limited set of resources, and...

Last time, we looked at building an AsyncCountdownEvent.  At the end of the post, I highlighted a common pattern for using such a type, which is for all of the participants to signal and then wait for all of the other participants to signal as well.  This kind of synchronization is typically referred to as a “barrier,” and oft...

In my last two posts, I discussed building AsyncManualResetEvent and AsyncAutoResetEvent coordination primitives.  In this post, I’ll build on that to create a simple AsyncCountdownEvent.A countdown event is an event that will allow waiters to complete after receiving a particular number of signals.  The “countdown” come...

In my last post, I discussed building an asynchronous version of a manual-reset event.  This time, we’ll build an asynchronous version of an auto-reset event.A manual-reset event is transitioned to the signaled state when requested to do so (i.e. calling Set()), and then it remains in that state until it’s manually transitioned bac...