How to use with DI?

[pamidur]

How to use with DI?

[pamidur]

This is not a final solution for DI problem, we still work on it, but
let's see what options we have:

Option 1: Create and manage logger inside aspect:

This is quite easy provided you use global aspects. Global aspects are singletons by themselves. So everything you create in their constructor are singletons as well.

    [Aspect(Scope.Global)]
    public class LogAspect : Attribute
    {
        private readonly TelemetryClient_logger;

        public LogAspect(ILogger logger)
        {
            _logger = new TelemetryClient();
        }
...

You can still use Scope.PerInstance but then make sure you manage your instance TelemetryClient properly (e.g. create one in static constructor of an Aspect)

Option 2: Manage runtime objects with IoC container and inject all you need trough constructor:

You need a static class with a static method:

 public static object GetInstance(Type type)

Then tell your aspect to use this class as a factory (use can use Global scope as well):

    [Aspect(Scope.PerInstance, Factory = typeof(ApplicationServices))]
    public class LogAspect

Then request TelemetryClient from constructor

        private readonly TelemetryClient _logger;
        public LogAspect(TelemetryClient logger)
        {
            _logger = logger;
        }

Then you can use any IoC container to setup your services, in example below I use Microsoft.Extensions.DependencyInjection. It requires all services to be registered, so I had to register both LogAspect and TelemetryClient

                .AddTransient<LogAspect>()
                .AddSingleton<TelemetryClient>()

One thing to pay attention to is since Aspect has constructor injection, you can't have it as Attribute. so you need a separate Attribute like this:

    [Injection(typeof(LogAspect))]
    public class LogAttribute : Attribute
    {
    }

Full code below (you can copy/paste to experiment yourself):

    public static class ApplicationServices
    {
        public static readonly ServiceProvider ServiceProvider;

        static ApplicationServices()
        {
            ServiceProvider = new ServiceCollection()
                .AddTransient<LogAspect>()
                .AddSingleton<TelemetryClient>()
                .BuildServiceProvider();
        }

        public static object GetInstance(Type type) => ServiceProvider.GetRequiredService(type);
    }


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

    [Log]
    public class TestClass
    {
        public void Do() { }
    }

    [Injection(typeof(LogAspect))]
    public class LogAttribute : Attribute
    {
    }

    [Aspect(Scope.PerInstance, Factory = typeof(ApplicationServices))]
    public class LogAspect
    {
        private readonly TelemetryClient _logger;

        public LogAspect(TelemetryClient logger)
        {
            _logger = logger;
        }

        [Advice(Kind.Before)]
        public void LogEnter([Argument(Source.Name)] string name)
        {
            _logger.TrackEvent($"Calling '{name}' method...");	
        }
    }

[shuizhugeju]

@pamidur
Great.
But if the instance can be passed from the constructor like the following code. so they can have the same Container and scope.

public class TestClass
	{
		// Token: 0x0600000D RID: 13 RVA: 0x0000223A File Offset: 0x0000043A
		public TestClass(LogAspect logAspect)
		{
			this.xxxxLogAspect= logAspect. //change the constractor.
		}

		// Token: 0x0600000C RID: 12 RVA: 0x00002227 File Offset: 0x00000427
		[Log]
		public void Do()
		{
			this.xxxLogAspect.LogEnter("Do");
		}


		protected LogAspect xxxLogAspect;
	}

[pamidur]

Unfortunately we can't modify constructors this way :( It would break contracts between different assemblies. But the instances can be created in the same scope by DI framework if your Aspect is PerInstance