The folks over at InfoQ have graciously provided a nice list of technology that has been discontinued in .NET Core. You can find their original list here. They present the list without much opinion or color. In this blog post, I’d like to take a look at that list from the point of view of someone considering using ASP.NET Core for cloud native application development.

Reflection

Reflection isn’t gone, it’s just changed a little bit. When you make things designed to work on multiple operating systems without having to change your code, some of your original assumptions about the code no longer apply. Reflection is one of those cases. Throughout my career, the majority of the times I’ve used Reflection in a running, production application have either been for enhanced debug information dumps in logs, or, to be honest, I was working around a complex problem in entirely the wrong way.

If you find yourself thinking that you need reflection for your .NET microservice, ask yourself if you really, really need it. Are you using it because you’re adopting some one-off, barely supported serialization scheme? Are you using it because you’re afraid your regular diagnostics aren’t good enough? I would be shocked if I ever had to use Reflection in 2016 directly when .NET Core already provides me with JSON and XML serializers.

App Domains

Manipulating application domains is something that I would consider a cloud native anti-pattern. Historically, we’ve used AppDomains for code and data isolation and as a logical unit of segmentation for CAS (Code Access Security). If your deployment target is the cloud (or basically any PaaS that uses container isolation), then I contend you should have nothing in your app that does any kind of AppDomain shenanigans. In fact, from the original article, here’s a quote from Microsoft:

For code isolation, we recommend processes and/or containers

Remoting

Ah, Remoting, how do I hate thee? Let me count the nearly infinite ways… The following statement from InfoQ’s article makes me feel old. VERY old.

These days few developers even remember the Remoting library exists, let alone how to use it.

Not only do I remember how to use it, but I wrote entire chapters for popular books on using Remoting. I’ve written custom communication channels for Remoting, implemented distributed trace collection systems that predate Splunk, and other things I shall not admit publicly… all with Remoting.

The bottom line is there is no place for a technology like Remoting in an ecosystem of services all scaling elastically and moving dynamically in the cloud. It’s dinosaur tech and those of us who used to write code against it for a living are likely also dinosaurs.

You’re not going to need this in the cloud, so it’s absence from .NET Core is a blessing.

Serialization

Most of the tools you need for serialization are still there. Binary serialization is one of those ugly things that used to go deep into the bowels of your objects, even private members, and convert POCOs into state that way.

If you need high-performance binary/byte array serialization of your .NET classes, use protocol buffers. You can use them from .NET Core.

If you’re doing more traditional service-to-service communication, then you’ll be just fine with JSON and XML. As far as building services for the cloud, you should be blissfully unaware of most serialization gaps between ASP.NET 4.x and .NET Core.

Sandboxing

Sandboxing is something that has traditionally had strong, low-level OS ties. This makes its implementation in a cross-platform framework a little more complicated and subject to least common denominator culling. If you’re just building services, you should be fine, but there’s a sentence in the InfoQ article that is decidedly not cloud-native:

The recommended alternative is to spawn separate processes that run under a user account with restricted permissions

This is not something you should be doing in the cloud. As a cloud native developer, you should be unconcerned with the identity with which your application process runs – this is a detail that is abstracted away from you by your PaaS. If you need credentials to access a backing service, you can deal with that using bound resources or bound services, which is all externalized configuration.

Sandboxing as the article describes isn’t something you should be doing when developing services for the cloud, so you should hopefully be well insulated from any of the changes or removals in .NET Core related to this.

Miscellaneous

There are a handful of miscellaneous changes also mentioned by the InfoQ article:

  • DataTable/DataSet – I feel so. very. old. Many of you will likely have no idea what these things are. This is how your grandparents communicated with SQL data sources prior to the invention of Entity Framework, nHibernate, or LINQ to SQL. That’s right, we wrote code uphill both ways in the snow. Get off my lawn. You will not need these in the cloud.
  • System.DirectoryServices – For some pretty obvious reasons, this doesn’t exist. You shouldn’t need to use this at all. If you need to talk to LDAP, you can do so using simpler interfaces or, better yet, through a token system like OAuth2.
  • System.Transactions – Distributed transactions, at least the traditional kind supported by libraries like this, are a cloud-native anti-pattern. Good riddance.
  • XSL and XmlSchema – Ok, so these might still be handy and I can see a couple types of services that might actually suffer a bit from their absence in the framework. Good news is that .NET Core is open source, so if enough people need this, either Microsoft or someone else will put it in.
  • System.Net.Mail – If you need to send mail from your cloud native service, you should consider using a brokered backing service for e-mailing. Just about every PaaS with a service marketplace has some kind of cloud-based mailing system with a simple REST API.
  • System.IO.Ports – I’m fairly certain you should not be writing code that communicates with physical serial ports in your cloud native service.
  • Workflow – Windows Workflow Foundation is also gone from .NET Core. Good riddance. I did a tremendous amount of work with that beast, and I tried harder than most mere mortals to like it, to embrace it, and to use it for greatness. I was never pleased with anything I produced in WF. The amount of hacky statefulness required to get it working would have immediately put this tech onto the cloud native naughty list anyway.
  • XAML – You do not need XAML to build a cloud service, so this is also no big loss.

Conclusion

The bottom line is that, aside from a few high-friction experiences in the current release candidate, the feature set of ASP.NET Core contains everything you need right now to build microservices for the cloud. The biggest concern isn’t what isn’t in .NET Core, it’s what third party libraries for accessing backing services are either missing or not ready for prime time. That’s where I see the risk in early adoption, not in the core feature set of the framework.