zenakuten / CoreAOP

Aspect oriented programming for .NET Core

CoreAOP

Aspect oriented programming using .NET Core and Microsoft's Dependency Injection.

This library allows you to extend interface functionality by defining and applying attributes to interfaces.

[Profile]
public interface IMyService 
{
    [Log]
    bool MyMethod();
}

Attributes are defined by implementing a base class

public abstract class AspectAttribute : Attribute, IAspect
{
    public virtual void OnCreate(Type createdType) { }
    public virtual object[] OnEnter(MethodInfo mi, object[] args) { }
    public virtual void OnException(MethodInfo mi, Exception ex) { }
    public virtual object OnExit(MethodInfo mi, object[] args, object retval) { }
}

Examples

public class LogAttribute : AspectAttribute
{
    public override void OnEnter(MethodInfo mi, object[] args) 
    { 
        Console.WriteLine($"Calling {mi.Name}");
        return args;
    }
}

public class ProfileAttribute : AspectAttribute
{
    private DateTime timestamp;
    public override void OnEnter(MethodInfo mi, object[] args) 
    { 
        timestamp = DateTime.Now;
        return args;
    }
    public override object OnExit(MethodInfo mi, object[] args, object retval) 
    { 
        Console.WriteLine($"Calling {mi.Name} took {DateTime.Now - timestamp}");
        return retval;
    }
}

The aspects are applied by extending IServiceCollection.

using Microsoft.Extensions.DependencyInjection;

 var services = new ServiceCollection();
 services.AddTransient<IMyService, MyService>();
 services.AddAspects();

^{AddAspects() must be called after your services with aspect attributes have been added to the collection.}

---

You can also add aspects by implementing the IAspect interface.

using Microsoft.Extensions.DependencyInjection;

public class MyAspect : IAspect
{
    public void OnCreate(Type createdType) { }
    public object[] OnEnter(MethodInfo mi, object[] args) 
    { 
        Console.WriteLine("MyAspect"); 
        return args;
    }
    public void OnException(MethodInfo mi, Exception ex) { }
    public object OnExit(MethodInfo mi, object[] args, object retval) 
    {  
        return retval; 
    }
}

 var services = new ServiceCollection();
 services.AddTransient<IMyService, MyService>();
 services.AddAspect<IMyService, MyAspect>();

The implementation is achieved using DispatchProxy