Wednesday, September 25, 2013

Enterprise Library 6 - SLAB - Supporting Complex Types for Payload

Previously we have discussed there are only certain primitive types supported by EventSource introduced in .net framework 4.5. This post is an attempt how we can work around this limitation. Actually, we can decorate EventSource methods with [Event] and [NonEvent] attributes. The other most important point is the following:

[Event] methods can be private.

We can use this to only include private [Event] methods which would be used to generate ETW manifest from the EventSource. Additionally we can introduce public methods in the EventSource type supporting the non-primitive custom type as parameters. Hence these object-oriented types make writing the logs easier without putting any load on the underlying infrastructure supporting the event mechanism.

Let's create a sample C# project targeting .net framework 4.5. We add a type EventSourceWithComplexType to the project. As you can see below this is an EventSource. Here we are using Lazy initialization introduced in .net framework 4.0 for singleton implementation [Please refer here for singleton implementation]. It has a private constructor to make sure that it cannot be instantiated from outside. The most noticeable thing is its two methods. Here we have a method StudentCreatedCore() decorated with [Event] attribute, has a list of parameters including types supported by the ETW infrastructure. It has a corresponding StudentCreated() method with [NonEvent] attribute. It has a public access modified and has a non-primitive type for parameter. The most important thing is that it is using the StudentCreatedCore() method.

Can The implementation satisfy EventSourceAnalyzer?
We have discussed that we can use EventSourceAnalyzer for testing our EventSource implementation [Discussion]. Let's see if we can satisfy EventSourceAnalyzer for the above implementation. We just need to call InspectAll() method with an instance of the EventSource. Here we are using xUnit for testing supported by resharper. You need to install the nuget package. You would also need to get EnterpriseLibrary.SemanticLogging package for using EventSourceAnalyzer.

As a matter of fact, EventSourceAnalyzer has no complaints and the unit test passes. Zindabad!

Listening for Events
Now let's see if we can listen for events using this EventSource implementation. Here we are attaching the EventSource with ConsoleSink using the ConsoleLog [Discussion]. We are using the same EventLister to enable the events. Here we are just using the public method on EventSource type with an instance of Student type. Let's see if we could see the event's data on the console [keep the spirit high, friend!!!].

And we do see that event's data is being printed on the console in the same format as we provided in the StudentCreatedCore() method. Hence the runtime was able to do it from the private method. It has no problem with generating the ETW manifest for private [Event] methods and using it at run-time. Zindabad!


Love for other people what you love for yourself.    [Prophet Muhammad - Salallahu-Alaihe-Wasallam]

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