Inject App Insights for Custom Events and Metrics

Question

What is the "right" way to use custom events and metrics for app insights in ASP.NET Core with dependency injection? Is there a way to inject TelemetryClient?

Everything I can find instantiates the TelemetryClient directly and TelemetryClient doesn't implement an interface.

Answer 1

TelemetryClient is automatically injected to DI when you configure Application Insights using either .UseApplicationInsights() or AddApplicationInsights() methods. You can use constructor injection to get the TelemetryClient instance as shown below.

public class HomeController : Controller
{
    private TelemetryClient telemetry;

    public HomeController(TelemetryClient telemetry)
    {
        this.telemetry = telemetry;
    }

    public IActionResult Index()
    {
        this.telemetry.TrackEvent("HomePageRequested");
        return View();
    }
}

https://github.com/Microsoft/ApplicationInsights-aspnetcore/wiki/Custom-Configuration#track-custom-traceeventmetric

Answer 2

i'm not sure you need to do dependency injection for that part.

other dependency injected stuff, like .UseApplicationInsights() does the work to ensure application insights is configured, etc.

after that, code that would do custom events or metrics normally create a TelemetryClient on demand, set shared context on the instance, and then write events/metrics through it, via the TrackEvent, TrackMetric, etc methods. Presuming AI is correctly configured in other places, those new telemetry client instances will have other shared/preconfigured/injected settings ready to go.