serilog-logging-setup

Serilog Structured Logging Setup

Wire up Serilog in ASP.NET Core for structured (JSON) logs with enrichers, request logging, sensible levels, and sinks — correlated with your traces.

Input — point it at your project

Works on a target: a project or GitHub URL. Inspect current logging: grep -rn "UseSerilog\|ILogger\|Log.Logger\|AddSerilog" --include=*.cs <target>. If OTel is present, wire log/trace correlation.

Packages + wiring

dotnet add package Serilog.AspNetCore
dotnet add package Serilog.Sinks.Seq        # or Console/Elastic/etc.

builder.Host.UseSerilog((ctx, services, lc) => lc
    .ReadFrom.Configuration(ctx.Configuration)
    .ReadFrom.Services(services)
    .Enrich.FromLogContext()
    .Enrich.WithMachineName()
    .Enrich.WithProperty("service", "orders")
    .WriteTo.Console(new RenderedCompactJsonFormatter())   // structured JSON
    .WriteTo.Seq(ctx.Configuration["Seq:Url"]!));

app.UseSerilogRequestLogging();   // one tidy log line per request instead of the default noise

Structured logging done right

// GOOD: message template + properties (queryable)
logger.LogInformation("Order {OrderId} placed by {CustomerId} for {Total}", id, customerId, total);
// BAD: interpolated string (loses structure)
logger.LogInformation($"Order {id} placed");

What to set

• Levels — Information default, Warning for noisy frameworks, Debug only in dev. Configure via appsettings.
• Enrichers — machine, environment, and a correlation/trace id (see correlation-id-middleware).
• Request logging — UseSerilogRequestLogging for one structured line per request with status + duration.
• Trace correlation — include TraceId/SpanId so logs link to traces.

Principles

• Message templates, not interpolation — structure is the whole point of structured logging.
• Don't log secrets/PII. Be deliberate about what goes into properties.
• Log at the right level; Information for business events, Error with the exception object (not ex.Message).
• One sink for local (console JSON), one for aggregation (Seq/Elastic/Loki).