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Derek Comartin

How to get started with CQRS & Event Sourcing

When I first heard about CQRS & Event Sourcing concepts through various blogs and videos, primarily from Greg Young and Udi Dahan, I wanted to apply it everywhere. It seems really natural to want to take the limited knowledge we have about a new concept or technology and try and apply it to any problem. Most of us know this is a terrible idea, but we are so tempted to push the concepts on a problem that it just doesn’t fit. I realize I’m grouping CQRS and Event Sourcing together in this post.  Generally, if you are applying Event Sourcing then… Read More »How to get started with CQRS & Event Sourcing

Handling Async Await Exceptions

Async/Await There’s a ton of information about async await support in .NET 4.5.  I don’t want to go over all the best practices and gotchas in this post, but I did want to point out one common trend I’ve seen lately, which is handling async await exceptions. Await or forget about it Any async method that returns a Task or Task<T>, you should always await the result. If you do not await, any exceptions that occur in the calling method will be swallowed.  Essentially you are turning the method call into a fire and forget. Async Await Exceptions Example Below is a simple example that… Read More »Handling Async Await Exceptions

Mediator Pattern using MediatR and Unity

In a couple previous posts I’ve discussed using Query Objects instead of Repositories and the Mediator pattern.  I find creating query objects being used with the command pattern much cleaner than polluting repositories with a ton of query methods. The concept is nothing new as many people already use the command pattern in the context of executing commands/behavior following CQRS.   However, there is nothing wrong with using the same patterns for the query side. I’ve been using my own home grown solution of the mediator pattern in a few different projects but had nothing really formalized.  I was thinking about creating a simple library… Read More »Mediator Pattern using MediatR and Unity