Links

Changes

Swashbuckle is no longer actively maintained and has been remove from .NET 9 templates. OpenAPI in ASP.NET Core 9 Web API

Log

public class MyClass(ILogger<MyClass> logger)
{
    public void MyMethod()
    {
        // to optimize the performances, test if the log level is enabled
        if (logger.IsEnabled(LogLevel.Debug)) logger.LogDebug("Debug");
        logger.LogTrace("Trace");
        logger.LogInformation("Info");
        logger.LogWarning("Warn");
        logger.LogError("Error");
        logger.LogCritical("Fatal");
    }
}

appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",       // log level par défaut
      "Microsoft": "Warning",         // pour les loggers commençant par Microsoft
      "MyNamespace.MyClass": "Debug"  // pour les loggers de MyClass
    }
  }

Program.cs

builder.Logging.ClearProviders();  // remove all the providers: no more logs

The Log methods are synchronous.
There is no file log provider.

Log in Program.cs

Program.cs

// with app
app.Logger.LogInformation("message");

// before app
var loggerFactory = LoggerFactory.Create(loggingBuilder =>
{
    loggingBuilder.AddConsole();
    loggingBuilder.AddConfiguration(builder.Configuration.GetSection("Logging"));
});
var logger = loggerFactory.CreateLogger("Program");

Built-in logging providers

Console	VS code "DEBUG CONSOLE" tab In the console window when the app is run with dotnet run
Debug	Debug window when debugging in Visual Studio On Linux journal or /var/log/message or /var/log/syslog
EventSource	Event Tracing for Windows (ETW)
EventLog	Windows Event Log
TraceSource	System.Diagnostics.TraceSource libraries and providers ()
Azure App Service	text files in an Azure App Service app's file system and to blob storage in an Azure Storage account

Console

appsettings.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Error"  // default log level
    }
  },
  "Console": {
    "LogLevel": {
      "Default": "Information"  // overwrite log level
    },
    "FormatterName": "json"  // log in JSON format
  }
}

journal

mar 19 17:53:10 hostname logtest[29321]: fail: LogTest.Controllers.ItemController[0]
mar 19 17:53:10 hostname logtest[29321]:       Log message

mar 19 17:58:27 hostname logtest[29321]: fail: Microsoft.AspNetCore.Server.Kestrel[13]
mar 19 17:58:27 hostname logtest[29321]:       Connection id "...", Request id "...": An unhandled exception was thrown by the application.
mar 19 17:58:27 hostname logtest[29321]: System.Exception: exception message
mar 19 17:58:27 hostname logtest[29321]:    at LogTest.Controllers.ItemController.ThrowException() in /dev-path/LogTest/Controllers/ItemController.cs:line 41

apache log

access.log is well filled by each query
error.log is never filled

LoggerMessage

Use LoggerMessage over Logger extension methods to improve performances.

logger.LogInformation("Message: {Message}", message);

static partial class Log
{
    [LoggerMessage(Level = LogLevel.Information, Message = "Message: {Message}")]
    public static partial void LogRequest(ILogger logger, string Message);
}

Log.LogRequest(logger, message);

Configuration

Sources des settings par défaut dans l'ordre de lecture:

appsettings.json
appsettings.<EnvironmentName>.json (Development, Staging, Production)
UserSecrets in Development environment
Environment variables
Command-line arguments

ItemsController.cs

public class ItemsController(IConfiguration configuration) : ControllerBase
{
    [HttpGet]
    public IActionResult Get()
    {
        // recherche Key, si Key n'a pas été trouvé affecte default value à la variable value
        var value = Configuration.GetValue<string>("Key", "default value");
        var value = Configuration["Key"];

       // pour les connection strings
       configuration.GetConnectionString("SqlServer1")

       // dotnet add package System.Data.SqlClient
       var builder = new SqlConnectionStringBuilder(Configuration.GetConnectionString("SqlServer4")); // from appsettings.json
       builder.Password = configuration["DbPassword"]; // from secrets storage in Dev and appsettings.json in Prod 
       var connectionString = builder.ConnectionString;

appsettings.json

{
  "Key": "Value",
  "ConnectionStrings": {
    "SqlServer1": "Server=(localdb)\\MSSQLLocalDB;Database=MyDb;Integrated Security=True;MultipleActiveResultSets=True",
    "SqlServer2": "Server=(localdb)\\mssqllocaldb;Database=MyDb;Trusted_Connection=True;",
    "SqlServer3": "Server=localhost;Database=MyDb;User=sa;Password=pwd;",
    "SqlServer4": "server=localhost;database=MyDb;user=sa;",
    "MySql": "Server=localhost;Database=MyDb;User=root;Password=pwd;",
    "Sqlite": "Data Source=MyDb.db"
  },
  "DbPassword": "****"
}

Safe storage of app secrets in development in ASP.NET Core

User Secrets – What Are They And Why Do I Need Them?

Useful in dev environment to not store password in source code.

# aller dans le dossier contenant le *.csproj
cd MyProject

# adds a UserSecretsId element within a PropertyGroup of the .csproj file
dotnet user-secrets init

# set a secret
# put a space as first character so the command line is not saved in the history
 dotnet user-secrets set "key" "secret"
# the whole connection string
 dotnet user-secrets set "ConnectionStrings:SqlServer" "server=localhost;database=test;user=test;password=****"
# only the connection string password
 dotnet user-secrets set "DbPassword" "****"

# the secrets are stored in a JSON configuration file in a system-protected user profile folder on the local machine
# Windows: %APPDATA%\microsoft\UserSecrets\<userSecretsId>\secrets.json
# Linux:   ~/.microsoft/usersecrets/<userSecretsId>/secrets.json


# list all secrets of the current project
dotnet user-secrets list

# remove a secret in the current project
dotnet user-secrets remove "key"

# remove all secrets of the current project
dotnet user-secrets clear

Console/Program.cs

public static IConfigurationRoot Configuration { get; set; }

private static void Main()
{
    var builder = new ConfigurationBuilder();
    // dotnet add package Microsoft.Extensions.Configuration.UserSecrets
    builder.AddUserSecrets<Program>();
    Configuration = builder.Build();

Non-prefixed environment variables

/etc/systemd/system/kestrel-myapp.service

Environment=ConnectionStrings__MyApp=server\x3dlocalhost\x3bdatabase\x3dMyDb\x3buser\x3dMyUser\x3bpassword\x3dMyPwd
Environment=SqlServerVersion=10.10.5-MariaDB

Command-line

dotnet MyApp MyKey="value"

Publish

Framework-dependent executable

Creates a platform-specific executable with only the application binaries and its dependencies.

lighter deployment: only the application binaries and its dependencies are deployed
the .NET runtime security updates are managed by the system

the required .NET runtime of the application has to match the installed .NET runtime

dotnet publish -c Release -r linux-arm64 --self-contained false
# -c : configuration : Debug (default), Release
# -r <RUNTIME_IDENTIFIER> : publishes the application for a given runtime
# --self-contained [true|false] : publishes the .NET Core runtime with the application (default true if a runtime identifier is specified and the project is an executable project)
# -o /path/folder : output directory (default: bin/[configuration]/[framework]/[runtime]/publish )

dotnet publish

RID Catalog (list): linux-arm64, linux-x64, win10-x64

Self-contained deployment

Creates a platform-specific executable with the application binaries, its dependencies and the required .NET runtime.

runs on hosts which doesn't have the .NET runtime installed

bigger deployment
doesn't follow the .NET security updates

dotnet publish -c Release -r linux-arm64 --self-contained true -p:PublishTrimmed=true
# -c : configuration : Debug (default), Release
# -r <RUNTIME_IDENTIFIER> : publishes the application for a given runtime
# -o /path/folder : output directory (default: bin/[configuration]/[framework]/[runtime]/publish )

Trim self-contained deployments and executables

Linux

Service file

/etc/systemd/system/kestrel-myproject.service

[Unit]
Description=My Project description

[Service]
WorkingDirectory=/var/www/myproject
ExecStart=/var/www/myproject/MyProject
Restart=always
RestartSec=10  # Restart service after 10 seconds if dotnet service crashes
KillSignal=SIGINT
SyslogIdentifier=myproject
User=http
Environment=DOTNET_ROOT=/usr/share/dotnet8.0.4 ; to force a specific version of dotnet
Environment=ASPNETCORE_ENVIRONMENT=Production
Environment=DOTNET_PRINT_TELEMETRY_MESSAGE=false
Environment=ASPNETCORE_URLS=http://localhost:5001
Environment=ConnectionStrings__MyConnectionString=server\x3dlocalhost\x3bdatabase\x3dMyDb\x3buser\x3dMyUser\x3bpassword\x3dMyPwd
Environment=SqlServerVersion=10.10.5-MariaDB
Environment=MyWebapiUrl=http://localhost:5002

[Install]
WantedBy=multi-user.target

# escape value as connection string
systemd-escape "<value-to-escape>"