Options Pattern in .NET Core

When registering dependencies in the ConfigureServices method, you must have seen a pattern like the following code snippet.

services.AddDbContext<T>(options => options.UseSqlServer(**))
services.AddSwaggerGen(c => {
    c.SwaggerDoc(**);
})

This pattern is essentially an extension method on top of IServiceCollection, and the naming convention of this type of extension method is AddSomeService. The prototype of this method is like AddSomeService(this IServiceCollection services, Action<SomeOptions> action). The parameter action is a Lambda function, which can be used to provide extra configurations to the service.

In this blog post, we will create a similar service, MyService, that can be registered to the Dependency Injection (DI) container by calling the services.AddMyService(Action<MyServiceOptions> action) method. We will pass options to MyService so that this service can be more flexible with extra parameters at runtime. We will also take a look at the unit testing for MyService with its options.

The complete solution is located at this GitHub repository.

A must-read tutorial about the Options Pattern

Microsoft Docs has a detailed article about the Options Pattern in ASP.NET Core (link). This article covers…