Is it possible to add all IHostedService classes with a loop (ASP.NET Core 6)? - asp.net-core

Question

Is it possible to add all IHostedService implemented classes in a loop without adding them individually in ASP.NET Core 6?
Let's say we have this two implementations:
public class FirstImplementationOfHostedService : IHostedService
{
// ...
}
public class SecondImplementationOfHostedService : IHostedService
{
// ...
}
The default way in Program.cs to add them is:
builder.Services.AddHostedService<FirstImplementationOfHostedService>();
builder.Services.AddHostedService<SecondImplementationOfHostedService>();
But, what about having a hundred implementations?
There has to be a better way to add (at runtime) the one hundred implementations in Program.cs without explicitly spelling out all their names!

Answer 1

You can use an nuget package like this or you can create an extension method and get all references of services with reflection:
public static class ServiceCollectionExtensions
{
public static void RegisterAllTypes<T>(this IServiceCollection services,
Assembly[] assemblies,
ServiceLifetime lifetime = ServiceLifetime.Transient)
{
var typesFromAssemblies = assemblies.SelectMany(a =>
a.DefinedTypes.Where(x => x.GetInterfaces().Contains(typeof(T))));
foreach (var type in typesFromAssemblies)
services.Add(new ServiceDescriptor(typeof(T), type, lifetime));
}
}
and than call it at startup.cs
public void ConfigureServices(IServiceCollection services)
{
// ....
services.RegisterAllTypes<IInvoicingService>(new[] { typeof(Startup).Assembly });
}
But be careful , you are registering services in a collection. There is a long version of answer here. You should check.

Answer 2

You can use scrutor which does assembly scanning (which it seems like what you want) https://andrewlock.net/using-scrutor-to-automatically-register-your-services-with-the-asp-net-core-di-container/

Answer 3

The answer of #nzrytmn totally worked. Thank you very much!
I just made a few tweaks in RegisterAllTypes to fulfill my own requirements:
public static void RegisterAllTypes<T>(this IServiceCollection services)
{
var assemblies = new[] { Assembly.GetEntryAssembly() };
var typesFromAssemblies = assemblies.SelectMany(a => a?.DefinedTypes.Where(x => x.GetInterfaces().Contains(typeof(T))));
foreach (var type in typesFromAssemblies)
services.Add(new ServiceDescriptor(typeof(T), type, ServiceLifetime.Singleton));
}
Then in Program.cs:
builder.Services.RegisterAllTypes<IHostedService>();