How to share certain metadata between several aspects applied on the same object?

Question

I have these three aspects, applied on certain class:

[Serializable]
[MulticastAttributeUsage(PersistMetaData = true)]
public class MetaDataAspect : LocationInterceptionAspect, IInstanceScopedAspect
{
    public MetaData ThisMetaData = new MetaData();

    public object CreateInstance(AdviceArgs adviceArgs) { return MemberwiseClone(); }
    public void RuntimeInitializeInstance() {}
}

[Serializable]
[MulticastAttributeUsage(MulticastTargets.Method)]
public class CallInterceptionAspect : MethodLevelAspect, IMethodInterceptionAspect
{
    public void OnInvoke(MethodInterceptionArgs args){
        GetMetaData().ThisMetaData.Id = args.Arguments[0];
    }
}

[Serializable]
[MulticastAttributeUsage(MulticastTargets.Property)]
public class WmiClassPropertyAspect : LocationInterceptionAspect
{
    public override void OnGetValue(LocationInterceptionArgs args)
    {
        args.Value = GetMetaData().ThisMetaData.Id;
    }
}

How do I implement the GetMetaData() method so it gives me the ThisMetaData matadata?

Answer 1

Quick answer - introduce an interface and use it from method-level aspects.

Basically you need to do the following:

public interface IThisMetaDataProvider
{
    Metadata ThisMetadata {get;}
}

[Serializable]
[MulticastAttributeUsage(PersistMetaData = true)]
[IntroduceInterface(typeof(IThisMetadataProvider))]
public class MetaDataAspect : LocationInterceptionAspect, IInstanceScopedAspect
{
    public Metadata ThisMetadata {get; private set;}

    public void RuntimeInitializeInstance() { ThisMetadata = new Metadata(); }

    ...
}

[Serializable]
[MulticastAttributeUsage(MulticastTargets.Method)]
public class CallInterceptionAspect : MethodLevelAspect, IMethodInterceptionAspect
{
    public void OnInvoke(MethodInterceptionArgs args)
    {
        ((IThisMetadataProvider)args.Instance).ThisMetaData.Id = args.Arguments[0];
    }
}

You can also use IAspectProvider and IAspectRepositoryService (from 4.0 onward) to provide MetaDataAspect automatically to a class when CallInterception is used on a method.