I am pleased to announce that MSDN Magazine is doing a special issue this month on the new "async-await" feature that we are working on for the next versions of C# and Visual Basic. If this subject interests you, see my introductory article for beginners , Mads Torgersen's article on how it works behind...

Good morning everyone! I am pleased to tell you that the C# and VB teams are announcing a "refresh" of the async Community Technology Preview at MIX11 today, and that it is as of right now available on the Async CTP site . Recall that the CTP release is an early look at our thinking for the proposed...

(In this post I'll be talking about exogenous , vexing , boneheaded and fatal exceptions. See this post for a definition of those terms .) If your process experiences an unhandled exception then clearly something bad and unanticipated has happened. If its a fatal exception then you're already in no position...

Resuming where we left off (ha ha ha!) after that brief interruption: exception handling in "resumable" methods like our coroutine-like asynchronous methods is more than a little bit weird. To get a sense of how weird it is, you might want to first refresh your memory of my recent series on the design...

A number of people have asked me what motivates the design decision to require any method that contains an "await" expression to be prefixed with the contextual keyword "async". Like any design decision there are pros and cons here that have to be evaluated in the context of many different competing...

Suppose a city has a whole bunch of bank branches, each of which has a whole bunch of tellers and one gofer. There are a whole bunch of customers in the city, each of whom wants to withdraw a whole bunch of money from the bank at some varying time throughout the day. The algorithm goes like this: A customer...

Today I want to talk about asynchrony that does not involve any multithreading whatsoever. People keep on asking me "but how is it possible to have asynchrony without multithreading?" A strange question to ask because you probably already know the answer. Let me turn the question around: how is it possible...

I was walking to my bus the other morning at about 6:45 AM. Just as I was about to turn onto 45th street, a young man, shirtless, covered in blood ran down 45th at considerable speed right in front of me. Behind him was another fellow, wielding a baseball bat. My initial thought was "holy goodness, I...

I want to start by being absolutely positively clear about two things, because our usability research has shown this to be confusing. Remember our little program from last time? async void ArchiveDocuments(List<Url> urls) { Task archive = null; for(int i = 0; i < urls.Count; ++i) { var document...

The designers of C# 2.0 realized that writing iterator logic was painful. So they added iterator blocks. That way the compiler could figure out how to build a state machine that could store the continuation - the “what comes next” - in state somewhere, hidden behind the scenes, so that you don’t have...

Today is when things are going to get really long and confusing. But we'll make it through somehow. Consider the following task: you’ve got a list of URLs. You want to fetch the document associated with each URL. (Let’s suppose for the sake of argument that this always succeeds.) You then want to make...

The obvious question at this point is: if CPS is so awesome then why don’t we use it all the time? Why have most professional developers never heard of it, or, those who have, think of it as something only those crazy Scheme programmers do? First of all, it is simply hard for most people who are used...

Last time I sketched briefly how one might implement interesting control flows like try-catch using continuations; as we saw, the actual implementations of Try and Throw are trivial once you have CPS. I'm sure that you could extend that work to implement try-catch-finally. Or, another basic exercise...

Last time on Fabulous Adventures: “ But we can construct arbitrarily complex control flows by keeping track of multiple continuations and deciding which one gets to go next. ” Let’s look at an example of something more complex than a conditional. Consider a simplified version of “try-catch”, where there...

Good morning fabulous readers, let me just start by saying that this is going to get really long and really complicated but it will all pay off in the end. I’m also going to be posting on an accelerated schedule, more than my usual two posts per week. (It’ll eventually become clear why I'm doing all...