PostSharp: OnMethodBoundaryAspect on derived class's constructor

Question

Hi

I have an aspect that writes something to the console on exception. I have a base class that throws an exception on its constructor, and a derived class that have the aspect on its constructor.

I would expect that the derived class aspect on constructor will catch the base class exception, but it dont.

Is this by design? Is this a bug? Or am I doing something wrong?

Here is sample code (Console Application):

[Serializable]
public class OnExceptionWriteAspect : OnMethodBoundaryAspect
{
    public override void OnException(MethodExecutionEventArgs eventArgs)
    {
        Console.WriteLine("Exception catched on Aspect.");
    }
}

public class BaseClass
{
    public BaseClass()
    {
        throw new Exception();
    }
}

public class DerivedClass : BaseClass
{
    [OnExceptionWriteAspect]
    public DerivedClass()
        : base()
    {

    }
}

public class Program
{
    static void Main(string[] args)
    {
        try
        {
            new DerivedClass();
        }
        catch
        {
            Console.WriteLine("Exception catched on Main.");
        }
    }
}

The output is:

Exception catched on Main.

Answer 1

If you look at the DerivedClass via reflector you see that the Aspect only wraps the DerivedClass's constructor.

public class DerivedClass : BaseClass
{
    // Methods
    public DerivedClass()
    {
        MethodExecutionEventArgs ~laosEventArgs~1;
        try
        {
            ~laosEventArgs~1 = new MethodExecutionEventArgs(<>AspectsImplementationDetails_1.~targetMethod~1, this, null);
            <>AspectsImplementationDetails_1.MyTest.OnExceptionWriteAspect~1.OnEntry(~laosEventArgs~1);
            if (~laosEventArgs~1.FlowBehavior != FlowBehavior.Return)
            {
                <>AspectsImplementationDetails_1.MyTest.OnExceptionWriteAspect~1.OnSuccess(~laosEventArgs~1);
            }
        }
        catch (Exception ~exception~0)
        {
            ~laosEventArgs~1.Exception = ~exception~0;
            <>AspectsImplementationDetails_1.MyTest.OnExceptionWriteAspect~1.OnException(~laosEventArgs~1);
            switch (~laosEventArgs~1.FlowBehavior)
            {
                case FlowBehavior.Continue:
                case FlowBehavior.Return:
                    return;
            }
            throw;
        }
        finally
        {
            <>AspectsImplementationDetails_1.MyTest.OnExceptionWriteAspect~1.OnExit(~laosEventArgs~1);
        }
    }
}

public BaseClass()
{
    throw new Exception();
}

If you want to handle Aspect Inheritance look at using MulticastAttributeUsage

Answer 2

This is by design. There is no way to put an exception handler around the call to the base constructor. The MSIL code would not be verifiable.