CoreAOP 1.0.4

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