Skip to main content

DDD–Strongly typed Ids

One of the core principles of DDD is the usage of value objects to avoid “primitive obsession”. "Primitives" refer to the built-in types in C#,  int, string,guid etc. "Primitive obsession" refers to over-using these types to represent domain concepts that aren't a perfect fit. Some examples are a HouseNumber that is represented by an int or an EmailAddress that is represented by a string.

This concept not only makes sense for your value objects but is also valuable for your Entity and AggregateRoot id’s. A ProductId should not be interchangeable with an OrderId.

Creating a valueobject for every Id type is not that hard but remains cumbersome. Let’s introduce StronglyTypedId as a solution.

From the website:

StronglyTypedId makes creating strongly-typed IDs as easy as adding an attribute! No more accidentally passing arguments in the wrong order to methods - StronglyTypedId uses Roslyn-powered build-time code generation to generate the boilerplate required to use strongly-typed IDs.

Getting started

  • To get started, first add the StronglyTypedId nuget package to your project: https://www.nuget.org/packages/StronglyTypedId/
  • Now create a struct type and add the StronglyTypedId attribute on it.
    • Notice that we specify to not generate a JsonConverter. If you want to serialize the type you need to add an extra reference to Newtonsoft.Json or System.Text.Json.
  • Build your project. Let’s have a look at what is generated:
  • By default a Guid is used as the backing field. If you want to use a different type, you can specify this:

Popular posts from this blog

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.

.NET 8–Keyed/Named Services

A feature that a lot of IoC container libraries support but that was missing in the default DI container provided by Microsoft is the support for Keyed or Named Services. This feature allows you to register the same type multiple times using different names, allowing you to resolve a specific instance based on the circumstances. Although there is some controversy if supporting this feature is a good idea or not, it certainly can be handy. To support this feature a new interface IKeyedServiceProvider got introduced in .NET 8 providing 2 new methods on our ServiceProvider instance: object? GetKeyedService(Type serviceType, object? serviceKey); object GetRequiredKeyedService(Type serviceType, object? serviceKey); To use it, we need to register our service using one of the new extension methods: Resolving the service can be done either through the FromKeyedServices attribute: or by injecting the IKeyedServiceProvider interface and calling the GetRequiredKeyedServic...

Kubernetes–Limit your environmental impact

Reducing the carbon footprint and CO2 emission of our (cloud) workloads, is a responsibility of all of us. If you are running a Kubernetes cluster, have a look at Kube-Green . kube-green is a simple Kubernetes operator that automatically shuts down (some of) your pods when you don't need them. A single pod produces about 11 Kg CO2eq per year( here the calculation). Reason enough to give it a try! Installing kube-green in your cluster The easiest way to install the operator in your cluster is through kubectl. We first need to install a cert-manager: kubectl apply -f https://github.com/cert-manager/cert-manager/releases/download/v1.14.5/cert-manager.yaml Remark: Wait a minute before you continue as it can take some time before the cert-manager is up & running inside your cluster. Now we can install the kube-green operator: kubectl apply -f https://github.com/kube-green/kube-green/releases/latest/download/kube-green.yaml Now in the namespace where we want t...