Serilog

Structured event logging. Github: Getting Started · serilog/serilog Wiki (github.com)

dotnet add package serilog

dotnet add package serilog.sinks.consolePretty print to console.
dotnet add package serilog.sinks.fileLog to file.

Other Sinks Available: https://github.com/serilog/serilog/wiki/Provided-Sinks

creating loggers

Serilog.Core.Logger
Serilog.Ilogger
Serilog.Log

create root logger

Create this on application startup and then use it across classes:

using var log = new LoggerConfiguration()
  .MinimumLevel.Debug() // The minimum log level. If not specified, Information is used.
  .WriteTo.Console( // The WriteTo object configures sinks.
    AnsiConsoleTheme.Code, // 256-color VS Code inspired theme.
                           // Also: ConsoleTheme.None, SystemConsoleTheme.Literate (default), SystemConsoleTheme.Grayscale
    outputTemplate: "[{Level:u3}] [{Timestamp: HH:mm:ss}] {Message}{Newline}{Exception}")
  .WriteTo.File("path",
    new CompactJsonFormatter(), // Emit output as JSON instead of plaintext. See also: https://github.com/serilog/serilog/wiki/Formatting-Output#formatting-json
    rollingInterval: RollingInterval.Day,
    fileSizeLimitBytes: n, // Override the default (1GB) file size limit.
    retainedFileCountLimit: n, // Override the default (31) number of log files to keep.
    rollOnFileSizeLimit: true // Force roll over if the file size limit is met.
    outputTemplate: "{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] {Message:lj}{NewLine}{Exception}"),
    Message:lj // Output (l)iterals as is, the rest in (j)son.
    Level:u3 // Output the level names as 3-character (u)ppercase. Or: lo(w)ercase.
    Properties:j // Output additional context information as (j)son (or omit (j) for plain text).
    restrictedToMinimumLevel: LogEventLevel.Information) // Override the minimum debug level. Must be higher than the Logger's level.
  .CreateLogger();

Set the Global, Statically-Accessible Logger

This is not required.

Log.Logger = log;

Use the Logger

log.Information("Log entry");

Log Structured Data

var count = 456;
Log.Information("Retrieved {Count} records", count);

Output: { "Count": 456 }

var fruit = new[] { "Apple", "Pear", "Orange" };
Log.Information("In my bowl I have {Fruit}", fruit);

Output: { "Fruit": ["Apple", "Pear", "Orange"] }

destructuring

Use @ operator to pull values out of structured data:

var sensorInput = new { Latitude = 25, Longitude = 134 };  
Log.Information("Processing {@SensorInput}", sensorInput);  

// Extract only a subset of properties from a complex object:
Log.Logger = new LoggerConfiguration()
  .Destructure.ByTransforming<HttpRequest>(
    r => new { RawUrl = r.RawUrl, Method = r.Method })
    .WriteTo...

forcing stringification

Use $ operator to convert the property value to a string before any other processing takes place:

var unknown = new[] { 1, 2, 3 }
Log.Information("Received {$Data}", unknown); // Output: "System.Int32[]"

output templates

Log output templates are used by text-based sinks like console and file.
They are a superset of .NET format strings. Any valid string.Format() is accepted.

Built-in properties:
{Property:format specifier}

Exception - Full exception message and stack trace, multiple lines. Empty if no exception for the event.

Level - The log event level as the full level name.
:u letter level, uppercase.
:w letter level, lowercase.

Message

:l - Disables quoting of strings.
:j - Use JSON-style rendering for any structured data.
NewLine - System.Environment.NewLine

Properties - All other event properties that do not appear elsewhere in the output.

:j
Timestamp - As a DateTimeOffset

Tips

Escape { with another {
Name properties (like Count above) with PascalCase.
Log messages in fragments; avoid periods at end when possible.
Don’t:
- Log.Information("The time is " + DateTime.Now); This degrades performance and consumes cache memory.
Do:
- Log.Information("The time is {Now}", DateTime.Now);

shutdown

log.CloseAndFlush();

AppSettings Configuration

XML config file based configurations.

installation

dotnet add package serilog.settings.appsettings

reading config file

Log.Logger = new LoggerConfiguration()
  .ReadFrom.AppSettings()
  // … Other configuration
  .CreateLogger();

notes
.net
3rd party libraries
serilog