Program.cs

// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

using OpenTelemetry.Logs;
using OpenTelemetry.Resources;

var builder = WebApplication.CreateBuilder(args);

// Remove default providers and add OpenTelemetry logging provider.
// For instructional purposes only, disable the default .NET console logging provider to
// use the verbose OpenTelemetry console exporter instead. For most development
// and production scenarios the default console provider works well and there is no need to
// clear these providers.
builder.Logging.ClearProviders();

builder.Logging.AddOpenTelemetry(logging =>
{
    var resourceBuilder = ResourceBuilder
        .CreateDefault()
        .AddService(builder.Environment.ApplicationName);

    logging.SetResourceBuilder(resourceBuilder)

        // ConsoleExporter is used for demo purpose only.
        // In production environment, ConsoleExporter should be replaced with other exporters (e.g. OTLP Exporter).
        .AddConsoleExporter();
});

var app = builder.Build();

app.MapGet("/", (ILogger<Program> logger) =>
{
    logger.FoodPriceChanged("artichoke", 9.99);

    return "Hello from OpenTelemetry Logs!";
});

app.Logger.StartingApp();

app.Run();

internal static partial class LoggerExtensions
{
    [LoggerMessage(LogLevel.Information, "Starting the app...")]
    public static partial void StartingApp(this ILogger logger);

    [LoggerMessage(LogLevel.Information, "Food `{name}` price changed to `{price}`.")]
    public static partial void FoodPriceChanged(this ILogger logger, string name, double price);
}