Structured logging with Serilog for .NET 10 applications. Covers two-stage bootstrap, appsettings configuration, enrichers, sinks, request logging, destructuring, and Serilog.Expressions. Load this skill when setting up Serilog, configuring log sinks, enrichers, or structured logging, or when the us

Serilog Core Principles 1. Two stage initialization — Create a bootstrap logger for startup, then replace it with the full logger after DI is ready. This captures startup errors that would otherwise be lost. 2. AddSerilog() over UseSerilog() — Use builder.Services.AddSerilog() (the modern API) instead of builder.Host.UseSerilog() . It integrates with DI services via ReadFrom.Services(services) . 3. Message templates, not interpolation — {PropertyName} syntax creates structured data that can be queried. String interpolation ( $"..." ) breaks structure and allocates even when the log level is disabled. 4. Configure via appsettings.json — Keep log levels, sinks, and overrides in configuration so they can change per environment without redeployment. Patterns Two Stage Bootstrap Setup appsettings.json Configuration Override section uses namespace prefixes matched against SourceContext . More specific prefixes take precedence. Request Logging Middleware Replaces the multiple per request log events from ASP.NET Core with a single summary event. Structured Logging and Destructuring Scoped Properties with LogContext Requires .Enrich.FromLogContext() on the logger configuration. OpenTelemetry Sink (OTLP Export) Export Serilog events directly to any OTLP backend without the OpenTelemetry SDK: Serilog.Expressions for Filtering Requires the Serilog.Expressions package. [LoggerMessage] Source Generator for Hot Paths Built into Microsoft.Extensions.Logging.Abstractions — compile time generated, zero allocations when the level is disabled. Anti patterns Don't Use String Interpolation Don't Skip CloseAndFlush Don't Log Sensitive Data Don't Destructure Without Limits Don't Use the Deprecated Elasticsearch Sink Decision Guide Scenario Recommendation Application logging Serilog with AddSerilog() and appsettings.json Log storage (development) Seq (free single user) or Aspire Dashboard Log storage (production) Seq, Elasticsearch (Elastic sink), or OTLP backend Request logging UseSerilogRequestLogging() (replaces per request noise) Scoped properties LogContext.PushProperty() in middleware Log filtering Serilog.Expressions for expression based filtering High performance paths [LoggerMessage] source generator Audit trails AuditTo (synchronous, exceptions propagate) Log levels by environment MinimumLevel.Override per namespace in appsettings OpenTelemetry integration Serilog.Sinks.OpenTelemetry (no SDK dependency)

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