Stephen Toub

New Task APIs in .NET 4.6

February 2nd, 2015

There are several nice API-level enhancements to the Task Parallel Library in .NET 4.6, which you can grab a preview of as part of the Visual Studio 2015 CTP. Task.From* .NET 4.5 had a Task.FromResult method.  This method makes it quick and easy to manufacture a new Task for a known result value, and is particularly useful when implemen

.NET memory allocation profiling and Tasks

April 4th, 2013

The .NET Framework blog published this morning a guest post from yours truly on .NET Memory Allocation Profiling with Visual Studio 2012.  As you're trying to improve the performance, throughput, and memory usage of code that uses Tasks, the described profiler in Visual Studio can be a valuable tool in your tool belt (of course, the examp

Tasks, Monads, and LINQ

April 3rd, 2013

A few years back, Wes Dyer wrote a great post on monads, and more recently, Eric Lippert wrote a terrific blog series exploring monads and C#. In that series, Eric alluded to Task<TResult> several times, so I thought I’d share a few related thoughts on Task<TResult> and the async/await keywords.As both Wes and Eric highlight,

“Invoke the method with await”… ugh!

March 13th, 2013

I can be a bit sensitive when it comes to language and how concepts are conveyed.  I think it’s important to be accurate, even if not precise, when describing what something is or how to use it, as otherwise the folks to whom you’re communicating can easily form the wrong mental model for that thing.  Having a good mental

MVP Summit presentation on async

February 20th, 2013

Lucian Wischik and I presented an "async clinic" at the MVP Summit in Bellevue this week.  The async/await keywords in C# and Visual Basic drastically simplify asynchronous programming, but that of course doesn't mean that using them is without any gotchas: the goal of the discussion was to highlight some of the key areas in whi

Psychic Debugging of Async Methods

January 28th, 2013

These days it’s not uncommon for me to receive an email or read a forum post from someone concerned about a problem they’re experiencing with an async method they’ve written, and they’re seeking help debugging the issue.  Sometimes plenty of information about the bug is conveyed, but other times the communication i

Cooperatively pausing async methods

January 13th, 2013

Recently I was writing an app that processed a bunch of files asynchronously.  As with the Windows copy file dialog, I wanted to be able to provide the user with a button that would pause the processing operation.To achieve that, I implemented a simple mechanism that would allow me to pass a “pause token” into the async method

C# memory model articles

December 14th, 2012

Igor Ostrovsky is one of the minds behind the parallel programming support in the .NET Framework.  Igor's recently written a great set of articles for MSDN Magazine to cover "The C# Memory Model in Theory and Practice".  Part 1 is available now in the December 2012 issue, and it's a great read.

PLINQ and Int32.MaxValue

November 16th, 2012

In both .NET 4 and .NET 4.5, PLINQ supports enumerables with up to Int32.MaxValue elements.  Beyond that limit, PLINQ will throw an overflow exception.  LINQ to Objects itself has this limitation with certain query operators (such as the indexed Select operator which counts the elements processed), but PLINQ has it with more.This lim

How do I cancel non-cancelable async operations?

October 5th, 2012

This is a question I hear relatively frequently: “I have an async operation that’s not cancelable.  How do I cancel it?” The construction of the question often makes me chuckle, but I understand and appreciate what’s really being asked.  The developer typically isn’t asking how to cancel the operation