Writing to the log stream in a Window Azure App Service.

Program.cs

// This is a ASP.NET 6 sample showing how to write to the log stream in a Window Azure App Service.
// It seems standard out (stdout) is disabled in a Window Azure App Service.
// The key for me was adding the Microsoft.Extensions.Logging.AzureAppServices package
// To see logs in the Log Stream
// 1. go to "App Service logs" panel under monitoring
// 2. turn on Application logging (Filesystem)
// 3. set the level to Verbose or whatever is appropriate for the level of logging you want to see.
//    Note: This will automatically turn back off after 12 hours by design.
// 4. Now you can see the logs in the Log Stream panel of your App Service.

var builder = WebApplication.CreateBuilder(args);

// You need to add the Microsoft.Extensions.Logging.AzureAppServices packge
// dotnet add package Microsoft.Extensions.Logging.AzureAppServices
builder.Logging.AddAzureWebAppDiagnostics();

var app = builder.Build();

app.MapGet("/", () => {

    var logger = app.Services.GetService<ILogger<Program>>();
    logger?.LogInformation("This is visible in the Log Stream.");

    return "Hello world";
});

app.Run();