Wow! What a turnout for my first webinar! Thank you all for attending, I had a great time presenting it, and will continue to do more webinars in the future. The webinar was recorded, and the video is now online for your viewing:

As promised, here are the answers to the great questions you asked, which I didn’t have the chance to answer during the live webinar. As always, you can always ask your questions on our Support Forums.

Q: Any reason the [aspect] class must be Serializable?

A: At (post) compilation, the aspect is serialized using binary serialization, and added as a resource to the target process. Then at runtime, the aspect is deserialized. PostSharp will emit a compilation error if you forget to mark your aspect as Serializable.

Q: What is the typical use case for creating interfaces using PostSharp?

A: One typical scenario for implementing interfaces with PostSharp is implementing INotifyPropertyChanged in WPF to support Data Binding.

Q: Are the OnExit and OnEnter aspects thread safe? How would one make it thread safe if it is not?

A: While the aspects themselves are thread-safe, shared state (i.e. custom fields) within the aspects is not. To safely pass data around between OnEnter and OnExit events, you can use the MethodExecutionArgs.MethodExecutionTag property.

Q: What about signed DLLs and PostSharp?

A: PostSharp has no problems with signed DLLs – they will be re-signed after the post-compilation process.

Q: What about Silverlight DLL's, is it also available?

A: Of course, PostSharp comes with the Silverlight assemblies included, you need to add a reference to the PostSharp.SL.dll instead of PostSharp.dll. For more information, please refer to the online documentation.

Q: Can you provide a good definition of aspect oriented programming?

A: Aspect Oriented Programming complements traditional OOP by allowing us to encapsulate infrastructure code (such as logging, security, validation, etc.) into small modules called aspects, and then apply those aspects throughout the entire system in such way that the business logic is completely separated from those concerns.

So go ahead, download the free starter edition now!

Happy PostSharping!


Boilerplate code. It’s all around us, polluting our business logic, and forcing us to write the same code over and over again. Join us on Thursday, January 26th, as our very own Igal Tabachnik shows you how to stay DRY (Don’t-Repeat-Yourself) by using aspect-oriented programming (AOP) and PostSharp to remove boilerplate code that’s duplicated in and across systems.

Attendees will learn:

  • Why the DRY principle matters
  • How AOP helps to remove boilerplate code
  • How to use PostSharp to produce cleaner code
  • Real-world AOP usage examples

Oh, and that’s not all – we’re giving away two PostSharp licenses to two lucky attendees!

So hurry up, sign up here:

During compilation, PostSharp takes great care in making sure that everything works correctly. When something goes wrong, PostSharp will report it as an error or a warning. Until now, however, whenever an error or a warning occurred, the developer had to manually navigate to that place in code.

We are excited to announce that with PostSharp 2.1 we’ve enhanced the errors and warnings with the exact location information, allowing you to simply double-click on the message and you’ll be taken to the error line!

To enable this feature, go to Tools – Options – PostSharp, and under Experimental, set Resolve Message Location to True:

Then, simply rebuild your solution, and if there are any warnings or errors, you’ll be able to see exactly where they are:

This is accomplished by specifying the member (in this case, the method) that is responsible for the message, in the aspect’s CompieTimeValidate method:

// Validate the attribute usage.
public override bool CompileTimeValidate( MethodBase method )
    // Don't apply to constructors.
    if ( method is ConstructorInfo )
        Message.Write( method, SeverityType.Error, "CX0001", 
                       "Cannot cache constructors." );
        return false;

    MethodInfo methodInfo = (MethodInfo) method;

    // Don't apply to void methods.
    if ( methodInfo.ReturnType.Name == "Void" )
        Message.Write( method, SeverityType.Error, "CX0002", 
                       "Cannot cache void methods." );
        return false;

    // Does not support out parameters.
    ParameterInfo[] parameters = method.GetParameters();
    for ( int i = 0; i < parameters.Length; i++ )
        if ( parameters[i].IsOut )
            Message.Write( method, SeverityType.Error, "CX0003", 
                           "Cannot cache methods with return values." );
            return false;

    return true;

Aspect developers are encouraged to include the member in error/warning messages. For more information, please refer to the documentation on Working with Errors, Warnings and Messages.

Please note that this is not enabled by default as it is still experimental and might have an impact on performance. Please let us know how it works out for you!

Happy PostSharping!