I’m pleased to announce the second release candidate of PostSharp 2.1, available for download today on our web site and on NuGet. The first RC proved to be very stable, so this new version contains only relatively minor bug fixes. This RC also contains all bug fixes from the 2.0 branch.

Here’s the list of bugs that have been fixed in this release:

  • CopyCustomAttributes causes exception when several types are passed to the constructor
  • Fields are not visible by the debugger when a class has been moved to a binding class
  • ImageWriter sets the section virtual size to an invalid value, causing failure in Windows Phone
  • Invalid code generation when introducing a property or event of an open generic type
  • Invalid code generation when introducing a property with a private property setter
  • MainForm.CloseNotificationIcon throws InvalidOperationException after hibernation
  • MSBuild failure when building a project on a FAT system (hard links not supported)
  • PostSharp HQ throws exception when saving a license key for all users
  • Setup program displays maintenance dialog when in silent mode
  • Setup program prompts to uninstall previous version of the VS extension even in silent mode
  • The license registration wizard should not be displayed after a silent installation.
  • Exception in MulticastAtributeTask when a parameter-level MulticastAttribute is applied to a property
  • Unused AssemblyRefs are included in the final assembly
  • MulticastAttribute.TargetMemberAttributes is not respected for properties and events

PostSharp 2.1 is the fastest and most stable version of PostSharp and the upgrade is recommended for any one. To convert your projects, either use NuGet, either open PostSharp HQ and click on convert projects.

We’re now planning for PostSharp 3 and a new, truly disruptive, product that will change the landscape of instrumentation and diagnostic of in-production applications. We are hiring; drop us an email if you’re interested in joining the team.

Happy PostSharping!


This is one of these unpopular but necessary decisions that every software publisher has to do now and then. It’s generally accepted that pulling off expensive but little-used features is a healthy decision because it frees resources that can be spent on more popular features. This is what we are doing with documentation and support of PostSharp SDK.

What is PostSharp SDK?

PostSharp is made of two principal components: PostSharp.dll and PostSharp.Sdk.dll.

PostSharp.dll is the high-level public API. It mostly contains interface definitions, abstract classes and custom attributes from which developers can derive their own aspects. This library is designed to be used by developers of business applications. It offers transformation primitives (such as: intercepting a method, wrapping a method, introducing an interface) that developers can add to their code.  PostSharp.dll leverages real aspect-oriented programming, a disciplined extension of object-oriented programming. Just as a normal compiler, the high-level API enforces syntactic rules, and you will get a reasonable error message if you violate them.

PostSharp.Sdk.dll is the opposite of PostSharp.dll. Its public API allows you to modify .NET assemblies at a very low level. You can do everything. The API does not enforce any programming discipline or syntactic rules. You can create invalid assemblies without even getting a warning. It requires you to learn the MSIL specification and to understand most of the 565 pages of the ECMA-335 specification. PostSharp.Sdk.dll is made of several components. The most low-level ones (code model, image reader, image writer) are also found in Mono Cecil and Microsoft CCI, although PostSharp SDK has its own implementation. PostSharp SDK also includes several middle-level components such as the project loader, the aspect infrastructure (which could allow you to use PostSharp SDK to develop an aspect weaver that has different syntax than PostSharp.dll), the aspect weaver (the implementation of the PostSharp.dll), the custom attribute multitasking components, and much more.

PostSharp SDK is more complex than you think

Contrarily to PostSharp itself, PostSharp SDK has a very steep, but misleading, learning curve. You get quite quickly the illusion that you “got” it, but the devil is in details. The 80-20 rules does not apply to PostSharp SDK: what applies is 95-5: 95% of time is spent in addressing 5% of cases. Think of MSIL programming as hiking in high mountains without a map. You always have the illusion that the top is near, but whenever you climb on what appeared to be top, you discover another, higher top. If you want to have an idea of the effort you’ll need to reach the goal, you need a map; ECMA-335 and the PostSharp SDK class reference will give you a fair overview of the complexity of your task.

So why do we have PostSharp SDK? First, for our own needs. From our own point of view, PostSharp SDK is the most important component of PostSharp. Secondly, because this API is useful to a tiny minority of ISVs with very specific needs (for instance: high focus on speed). They can afford to maintain MSIL skills because the effort is leveraged to thousands of customers. Third, because PostSharp SDK can be used to overcome missing features of PostSharp.dll. But this is where things can go wrong.

PostSharp SDK is undocumented and unsupported

There has been some criticism that PostSharp SDK is undocumented. This is not accurate: the class reference is quite complete and contains more than what’s obvious from the method signature. Many actually claim that PostSharp SDK has the best documentation of all MSIL rewriting tools.

What is true is there is no conceptual documentation. Let me be clear: the lack of conceptual of documentation is a feature, not a defect. The SDK will not be better documented. As any company, we have to allocate limited resources to a potentially unlimited number of features. It does not economically make sense to spend time in documenting a very complex API that is used by a dozen of customers.

The same holds for support. We cannot provide support on a highly complex and incompletely documented API. We cannot guide you through baby steps. PostSharp SDK is not supported. You use it at your own risks.

Nostra Culpa

On the support forum, you could often read answers that sounded like “this is not possible to do with PostSharp.dll but can be done with PostSharp.Sdk.dll”, followed by a disclaimer that PostSharp SDK is hard and you should maybe not try. This had led some customers to ask for more information for these specific cases, which I published on the blog. Mistake! These blog posts have been interpreted as an advertisement of and an invitation to use PostSharp SDK. I apologize for that. I will not advertise PostSharp SDK again. It will remain unsupported and undocumented. The harmful blog posts have been withdrawn.

PostSharp SDK still available

That said, PostSharp SDK is still available for use in the Professional Edition. We are only making it clearer that this feature is not officially supported, and must be used at own risk. I believe that it’s not a good idea to code directly MSIL instructions unless you can leverage the effort to thousands of customers (as we do), but you’re free to try. It’s just that you’re on your own.

I’m aware this decision will be unpopular, but I’m convinced it’s a necessary one to continue provide good support to the community.

Happy PostSharping !


I’m excited to announce the first release candidate of PostSharp 2.1, available for download from our website and from the NuGet official repository.

PostSharp 2.1 is a minor upgrade of PostSharp 2.0; the upgrade is free for everybody. The objective of this version is to fix several gray spots in the previous release.

This release candidate is ought to be of very high quality and free of known bugs, but needs to be tested by the community before it can be labeled stable. As required by the RC quality label, the online documentation has been updated to reflect the latest API.

PostSharp 2.1 has full backward binary compatibility with PostSharp 2.0.

What’s new in RC 1?

This release candidates contains the following additions to the previous CTP:

  • The design of architecture validation (PostSharp.Constraints) has been finalized.
  • Warnings can be disabled locally (for a specific element of code) using the IgnoreWarning custom attribute. See online documentation for details.
  • The PostSharp project property page in Visual Studio now allows you to specify which warnings should be globally ignored or escalated into errors.
  • Compatibility with Code Contracts 4.0
  • As an experimental feature, warnings and errors now come with file/line information. The feature must be enabled manually from Visual Studio options. We’re eager to hear feedback about this feature from customers with larger projects.
  • 17 bug fixes

What’s new in PostSharp 2.1?

If you missed the previous announcements, here’s a list of new features in PostSharp 2.1 compared to version 2.0:

  • Improved build-time performance: up to 5x faster. Read more.
  • Architecture validation: build-time validation of design rules. Read more.
  • Extended reflection API: programmatically navigate code references. Read more and more.
  • NuGet packaging and improved no-setup deployment experience. Read more.
  • Support for obfuscators: we now support Dotfuscator. Read more.
  • Support for Silverlight 5.
  • Compatibility with Code Contracts 4.
  • Improved messaging API.
  • Tab page in Visual Studio project properties.
  • Streamlined licensing experience.
  • License server.
  • Streamlined “getting started” experience.

Upgrade your Projects

To upgrade your projects from PostSharp 2.0 to PostSharp 2.1 easily you can use the conversion utility included in the PostSharp HQ application. Just open the app and click on “convert”, then select the folder containing your projects. References to libraries and MSBuild imports will be automatically fixed.

PostSharp 2.1 Roadmap

A release candidate means that we are confident in the code quality and is that all mandatory quality work, including documentation, has been done. PostSharp 2.1 is now the default version on our download page. We’ll wait a couple of weeks to allow the community to give this version a try, then publish the RTM or another RC, according to the feedback.

Note that the license agreement allows for production use.

It’s now time to download PostSharp 2.1 and upgrade your projects!

Happy PostSharping!