Setting useLegacyV2RuntimeActivationPolicy At Runtime
Version 4.0 of the .NET Framework included a new CLR which is almost entirely backwards compatible with the 2.0 version of the CLR. However, by default, mixed-mode assemblies targeting .NET 3.5sp1 and earlier will fail to load in a .NET 4 application. Fixing this requires setting useLegacyV2RuntimeActivationPolicy in your app.Config for the application. While there are many good reasons for this decision, there are times when this is extremely frustrating, especially when writing a library. As such, there are (rare) times when it would be beneficial to set this in code, at runtime, as well as verify that it’s running correctly prior to receiving a FileLoadException.
Async CTP Refresh for Visual Studio 2010 SP1 Released
The Visual Studio team today released an update to the Visual Studio Async CTP which allows it to be used with Visual Studio SP1. This new CTP includes some very nice new additions over the previous CTP. The main highlights of this release include:
- Compatibility with Visual Studio SP1
- APIs for Windows Phone 7
- Compatibility with non-English installations
- Compatibility with Visual Studio Express Edition
- More efficient Async methods due to a change in the API
- Numerous bug fixes
- New EULA which allows distribution in production environments
Anybody using the Async CTP should consider upgrading to the new version immediately. For details, visit the Visual Studio Asynchronous Programming page on MSDN.
ConcurrentDictionary<TKey,TValue> used with Lazy<T>
In a recent thread on the MSDN forum for the TPL, Stephen Toub suggested mixing ConcurrentDictionary<T,U> with Lazy<T>. This provides a fantastic model for creating a thread safe dictionary of values where the construction of the value type is expensive. This is an incredibly useful pattern for many operations, such as value caches.
Parallelism in .NET – Part 20, Using Task with Existing APIs
Although the Task class provides a huge amount of flexibility for handling asynchronous actions, the .NET Framework still contains a large number of APIs that are based on the previous asynchronous programming model. While Task and Task<T> provide a much nicer syntax as well as extending the flexibility, allowing features such as continuations based on multiple tasks, the existing APIs don’t directly support this workflow.
Parallelism in .NET – Part 19, TaskContinuationOptions
My introduction to Task continuations demonstrates continuations on the Task class. In addition, I’ve shown how continuations allow handling of multiple tasks in a clean, concise manner. Continuations can also be used to handle exceptional situations using a clean, simple syntax.
Parallelism in .NET – Part 18, Task Continuations with Multiple Tasks
In my introduction to Task continuations I demonstrated how the Task class provides a more expressive alternative to traditional callbacks. Task continuations provide a much cleaner syntax to traditional callbacks, but there are other reasons to switch to using continuations…
Parallelism in .NET – Part 17, Think Continuations, not Callbacks
In traditional asynchronous programming, we’d often use a callback to handle notification of a background task’s completion. The Task class in the Task Parallel Library introduces a cleaner alternative to the traditional callback: continuation tasks.
Parallelism in .NET – Part 16, Creating Tasks via a TaskFactory
The Task class in the Task Parallel Library supplies a large set of features. However, when creating the task, and assigning it to a TaskScheduler, and starting the Task, there are quite a few steps involved. This gets even more cumbersome when multiple tasks are involved. Each task must be constructed, duplicating any options required, then started individually, potentially on a specific scheduler. At first glance, this makes the new Task class seem like more work than ThreadPool.QueueUserWorkItem in .NET 3.5.
In order to simplify this process, and make Tasks simple to use in simple cases, without sacrificing their power and flexibility, the Task Parallel Library added a new class: TaskFactory.
MEF CompositionInitializer for WPF
The Managed Extensibility Framework is an amazingly useful addition to the .NET Framework. I was very excited to see System.ComponentModel.Composition added to the core framework. Personally, I feel that MEF is one tool I’ve always been missing in my .NET development.
Unfortunately, one perfect scenario for MEF tends to fall short of it’s full potential is in Windows Presentation Foundation development. In particular, there are many times when the XAML parser constructs objects in WPF development, which makes composition of those parts difficult. The current release of MEF (Preview Release 9) addresses this for Silverlight developers via System.ComponentModel.Composition.CompositionInitializer. However, there is no equivalent class for WPF developers.
Parallelism in .NET – Part 15, Making Tasks Run: The TaskScheduler
In my introduction to the Task class, I specifically made mention that the Task class does not directly provide it’s own execution. In addition, I made a strong point that the Task class itself is not directly related to threads or multithreading. Rather, the Task class is used to implement our decomposition of tasks.
Once we’ve implemented our tasks, we need to execute them. In the Task Parallel Library, the execution of Tasks is handled via an instance of the TaskScheduler class.
