Supercharge Your .NET Core Logging with OpenTelemetry Activities

When it comes to observability in modern distributed systems, structured and traceable logging is essential. OpenTelemetry has emerged as the standard for collecting distributed traces, metrics, and logs. In the .NET ecosystem, the System.Diagnostics.Activity class is the core of OpenTelemetry tracing—and integrating it into your app is easier than you might think.

In this article, we’ll walk through how to create and use Activity objects in your .NET Core app for better logging and tracing across services.

🧠 What Is an Activity?

An Activity represents a unit of work in your application, such as a web request, a database call, or an external API call. It captures:

• A unique ID (trace and span IDs)

• Start/stop timestamps

• Tags (key-value pairs)

• Events

• Links to other Activities

OpenTelemetry uses Activity as the underlying model for traces.

✅ Prerequisites

• .NET 6 or .NET 8 SDK

• Basic understanding of logging in .NET (ILogger)

• NuGet packages:
  dotnet add package OpenTelemetry
  dotnet add package OpenTelemetry.Exporter.Console
  dotnet add package OpenTelemetry.Extensions.Hosting

   

  🛠️ Step-by-Step: Using Activities in a .NET Core App

  1. Set Up OpenTelemetry in Program.cs

  First, configure OpenTelemetry to start collecting traces.

  using OpenTelemetry.Trace;
  using OpenTelemetry.Resources;

  var builder = WebApplication.CreateBuilder(args);

  builder.Services.AddOpenTelemetry()
  .WithTracing(tracing =>
  {
  tracing
  .SetResourceBuilder(ResourceBuilder.CreateDefault().AddService(“MyAwesomeApp”))
  .AddAspNetCoreInstrumentation()
  .AddHttpClientInstrumentation()
  .AddConsoleExporter(); // For demo purposes, export to console
  });

  builder.Services.AddControllers();
  var app = builder.Build();

  app.MapControllers();
  app.Run();

  This setup adds auto-instrumentation for HTTP requests and outputs traces to the console.

  OpenTelemetry’s Activity API is a powerful, low-overhead way to bring distributed tracing and structured logging to your .NET Core apps. Whether you’re tracking latency issues or just improving log correlation, Activity gives you the structure you need.

  • Use ActivitySource to create custom spans

  • Add tags, events, and use using to auto-stop

  • Configure OpenTelemetry to auto-instrument ASP.NET and HTTP

  • Enable logging correlation with ActivityTrackingOptions

  • Export traces to Jaeger, Zipkin, or the console

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