Can I dynamically generate an aspect before another aspect is run?

Question

I will try to phrase this question with as little details as needed, to keep the question brief. Let me know if more details are required.

I have an aspect X on property A which dynamically generates an aspect Y on property B. Property B may be already contain aspects of type Y, and these interact with each other and the generated instance of Y.

I require the instances of Y generated by X, to be present before the non-generated instances of Y are run. Using AspectDependencies I have not been able to make this work. I've place a AspectDependencyPosition.

The aspect dependency I've placed on X is of the form: [AspectTypeDependency(AspectDependencyAction.Order, AspectDependencyPosition.Before, typeof(Y))]

The execution order that I get is: SourceInstanceOfY,X,GeneratedInstanceOfY

While the execution order that I need is: X,SourceInstanceOfY,GeneratedInstanceOfY where the last two may change order.

Is there a way to solve this solution or it not supported by PostSharp?

Thanks, Remy.

Answer 1

By using AspectTypeDependency you specified the ordering between aspects X and Y, but the order for Y instances is still not specified. You can use the ApectPriority property to order individual instances of the Y aspect. You can find the simple example based on your description below:

class TestClass
{
    [MyAspectX]
    public int PropertyA { get; set; }

    [MyAspectY("from attribute", AspectPriority = 2)]
    public int PropertyB { get; set; }
}

[Serializable]
public class MyAspectX : LocationInterceptionAspect, IAspectProvider
{
    public override void OnGetValue(LocationInterceptionArgs args)
    {
        Console.WriteLine("X OnGetValue");
        base.OnGetValue(args);
    }

    public IEnumerable<AspectInstance> ProvideAspects(object targetElement)
    {
        yield return new AspectInstance(
            ((LocationInfo) targetElement).DeclaringType.GetProperty("PropertyB"),
            new MyAspectY("from provider") {AspectPriority = 1});
    }
}

[Serializable]
public class MyAspectY : LocationInterceptionAspect
{
    private string tag;

    public MyAspectY(string tag)
    {
        this.tag = tag;
    }

    public override void OnGetValue(LocationInterceptionArgs args)
    {
        Console.WriteLine("Y OnGetValue " + tag);
        base.OnGetValue(args);
    }
}

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine(new TestClass().PropertyB);
    }
}