Whenever I have a need to write a Windows Service, Topshelf is pretty much the first nuget package that I install to aid in the task. In a nutshell, Topshelf is a framework that makes writing Windows Services easier; you write a standard console application, add Topshelf to the mix and you now have an application that can be run as a console application whilst developing and debugging, and installed as a Windows Service when the need to deploy arises. It's a pretty frictionless experience, but there can be some a gotcha when using Topshelf in conjunction with MassTransit and Dependency Injection. I've experienced this a few times so thought I'd write it down here for next time!
I'm a fan of the Data Annotation Validation attributes to validate user input on both the client and server side for ASP.NET MVC applications. I'm also a fan of Inversion of Control and Dependency Injection to create loosely coupled and flexible applications. There are certain situations where one would wish to inject services into a validation attribute to use during validation; a (somewhat contrived and security cautious) example of this might be providing the user with a <select> element and ask them to choose an option from it and then validate that the option that they have chosen is one that actually exists for the type of items represented in the dropdown. Sure, the RemoteAttribute would allow you to call a server side method via AJAX to perform validation but it does not provide any server side validation, making it more of a convenience solution than a complete and robust one. What would be good is if we could
- provide services to a validation attribute that could be used in the process of validation
- Not have to explicitly resolve services from the container à la the Service Locator (Anti-)Pattern