Bits of .NET

📝 Serilog = Structured Logging

Text logs are hard to search. Serilog provides structured logging with rich data for better observability.

📝 Serilog Setup

// Program.cs
using Serilog;

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Information()
    .WriteTo.Console()
    .WriteTo.File("logs/app.log", rollingInterval: RollingInterval.Day)
    .WriteTo.Elasticsearch()
    .Enrich.WithProperty("Application", "MyApp")
    .Enrich.WithProperty("Environment", "Production")
    .CreateLogger();

var builder = WebApplication.CreateBuilder(args);
builder.Host.UseSerilog();

// appsettings.json
{
    "Serilog": {
        "Using": ["Serilog.Sinks.Console", "Serilog.Sinks.File"],
        "MinimumLevel": "Information",
        "WriteTo": [
            { "Name": "Console" },
            { 
                "Name": "File", 
                "Args": { 
                    "path": "logs/app.log", 
                    "rollingInterval": "Day" 
                }
            }
        ],
        "Enrich": ["FromLogContext", "WithMachineName", "WithThreadId"]
    }
}

🎯 Structured Logging

// Traditional (bad)
_logger.LogInformation($"User {user.Id} logged in at {DateTime.Now}");

// Structured (good)
_logger.LogInformation("User {UserId} logged in at {LoginTime}", 
    user.Id, DateTime.UtcNow);

// With context
_logger.LogInformation(
    "User {UserId} purchased {ProductName} for {Price:C}",
    user.Id, product.Name, product.Price);

// Error with details
try {
    // operation
} catch (Exception ex) {
    _logger.LogError(ex, 
        "Failed to process order {OrderId} for user {UserId}",
        order.Id, order.UserId);
}

// Using ForContext
var userLogger = _logger.ForContext("User", user);
userLogger.LogInformation("User logged in");

// Correlation IDs
using (_logger.BeginScope(new { CorrelationId = correlationId }))
{
    // All logs in this scope include CorrelationId
    _logger.LogInformation("Processing request");
}

// Timed operations
using var timer = _logger.BeginTimedOperation("Database query", 
    new { Query = sql, Parameters = parameters });
var result = await db.QueryAsync(sql, parameters);

💡 Logging Best Practices

• Use structured logging
• Include correlation IDs
• Log at appropriate levels
• Use property names consistently
• Don’t log sensitive data