Manual setup of OpenTelemetry with/without Microsoft.Extensions.Hosting in a Console application

Question

After seeing Aspire I have decided to see how OpenTelemetry, and i first created a console application following the docs on https://opentelemetry.io/docs/instrumentation/net/manual/.

However, when I tried to move it into an easier setup using the extensionsmethod available in OpenTelemetry.Extensions.Hosting i could not get it to work. I think I might just misunderstand something about how it works.

So I have this working console application, which outputs the Actitivy in the console:
public static class Program
{
    public const string SERVICE_NAME = "MyService";
    public const string SERVICE_VERSION = "1.0.0";

public static async Task Main(string[] args)
    {
        var serviceCollection = new ServiceCollection();

serviceCollection.AddSingleton(new ActivitySource(SERVICE_NAME));
        serviceCollection.AddSingleton();

var tracerProvider = Sdk.CreateTracerProviderBuilder().AddSource(SERVICE_NAME)
            .ConfigureResource(resource = resource.AddService(serviceName: SERVICENAME, serviceVersion: SERVICEVERSION))
            .AddConsoleExporter()
            .Build();
        serviceCollection.AddSingleton(tracerProvider);
        
        var services = serviceCollection.BuildServiceProvider();

var helloWorld = await services.GetRequiredService().HelloWorldMethod();
        Console.WriteLine(helloWorld);
        Console.WriteLine("Program ended");
    }
}

public class TestLogic(ActivitySource activitySource)
{
    private readonly ActivitySource _activitySource = activitySource;

public async Task HelloWorldMethod()
    {
        using var activity = _activitySource.StartActivity("HelloWorldMethod");
        await Task.Delay(1000);
        return "Hello World";
    }
}

I then tried using the Generic Host builder and it does not write the activity to the console:

public static class Program
{
    public const string SERVICE_NAME = "MyService";
    public const string SERVICE_VERSION = "1.0.0";

public static async Task Main(string[] args)
    {
        var builder = Host.CreateApplicationBuilder();
        builder.Services.AddSingleton();
        builder.Services.AddOpenTelemetry()
            .ConfigureResource(resourceBuilder = resourceBuilder.AddService(serviceName: SERVICENAME, serviceVersion: SERVICEVERSION))
            .WithTracing(tracerProviderBuilder = tracerProviderBuilder.AddConsoleExporter());
        builder.Services.AddSingleton(new ActivitySource(SERVICE_NAME));

var host = builder.Build();
        await host.StartAsync(); //Used as OpenTelemetry adds the HostedService "TelemetryHostedService"

var helloWorld = await host.Services.GetRequiredService().HelloWorldMethod();
        Console.WriteLine(helloWorld);
        Console.WriteLine("Program ended");
        await host.StopAsync();
    }
}
public class TestLogic(ActivitySource activitySource)
{
    private readonly ActivitySource _activitySource = activitySource;

public async Task HelloWorldMethod()
    {
        using var activity = _activitySource.StartActivity("HelloWorldMethod");
        await Task.Delay(1000);
        return "Hello World";
    }
}

Does anyone know why I don't see the Activity in the console output? Or maybe know how I should set the Generic Host example up?

Manual setup of OpenTelemetry with/without Microsoft.Extensions.Hosting in a Console application

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