Question

I want to be able to call a differnt method on my intercepted class by using PostSharp.

Say I have the following method in my PostSharp aspect:

    public override void OnInvoke(MethodInterceptionArgs args)
    {
        if (!m_featureToggle.FeatureEnabled)
        {
            base.OnInvoke(args);
        }
        else
        {
            var instance = args.Instance;
            instance.CallDifferentMethod(); //this is made up syntax
        }  
    }

The CallDifferentMethod() is another method within the class that has been intercepted. I can do some reflection magic to get the name of what I want to be called, but I can’t work out how to call that method on this instance of the class. I don’t want to spin up a new instance of the class

Any suggestions?

Answer 1

Are you casting args.Instace to your type? Based on what you wrote, I’d imagine that your “FeatureEnabled” should be defined through an interface.

public interface IHasFeature
{
  bool IsFeatureEnabled { get; set; }
  void SomeOtherMethod();
}

then use

((IHasFeature)args.Instance).SomeOtherMethod(); 

Then apply the aspect to that interface.

[assembly: MyApp.MyAspect(AttributeTargetTypes = "MyApp.IHasFeature")]

or on the interface directly

[MyAspect]
public interface IHasFeature

Update: Oops, Gael is right. Sorry about that. Use the CompileTimeValidate method to LIMIT the aspect at compile time.

public override bool CompileTimeValidate(System.Reflection.MethodBase method)
        {
            bool isCorrectType = (Check for correct type here)
            return isCorrectType;
        }

For more information, see my post http://www.sharpcrafters.com/blog/post/Day-9-Aspect-Lifetime-Scope-Part-1.aspx