ASP.NET Core 8.0: Keyed Services in Dependency Injection

There are often times that we have different implementations of an interface and we need to resolve a particular implementation when doing dependency injection.

With ASP.NET Core 8.0, we now have support for Keyed Services.

Consider the following interface and its implementations.

public interface IMyService
{
    string GetValue();
}
 
public class MyService1 : IMyService
{
    public string GetValue() => "MyService1";
}
 
public class MyService2 : IMyService
{
    public string GetValue() => "MyService2";
}

Now we can register these Services with keys as follows.

WebApplicationBuilder builder = WebApplication.CreateBuilder(args);
 
builder.Services.AddKeyedScoped<IMyService, MyService1>("service1");
builder.Services.AddKeyedScoped<IMyService, MyService2>("service2");

You can register Keyed services with other lifetimes as well (Transient and Singleton).

Now we can resolve a specific implementation by key using [FromKeyedServices] attribute.

From the constructor

// Note:
//    I am using Primary Constructor which is new with .NET 8.0
//    You can use the other constructor as well
public class MyClass([FromKeyedServices("service1")] IMyService myService)
{
    public string GetValue() => myService.GetValue();
}

From an API Endpoint

app.MapGet("/", ([FromKeyedServices("service2")] IMyService myService) =>
{
    return myService.GetValue();
});

Hope this helps.

Happy Coding.

Regards,

Jaliya