justinsaraceno/dotnet-core-logging-sample

DotNet Core logging sample

Dotnet Core Logging Sample

This is an example of logging simultaneously to the console and nLog from .NET Core.

This sample is an ASP.NET Core API site that shows:

• Making logging available within the Startup.cs class by pre-configuring logging from Program.cs.
• Demonstrating how to log from the Startup.cs class.
• Including the nLog logging provider.

---

##How to log events from within Startup.cs:

• Create an ASP.NET Core Web Application (this sample uses the Web API template).

• From Program.cs, configure logging and log to the console as shown here:

public class Program
{
	public static void Main(string[] args)
	{
		var host = new WebHostBuilder()
			.UseKestrel()
			.UseContentRoot(Directory.GetCurrentDirectory())
			.UseIISIntegration()
			.ConfigureLogging(f => f.AddConsole(LogLevel.Debug)) // initialize logging here to make the logger available in Startup.cs
			.UseStartup<Startup>()
			.Build();

		host.Run();
	}
}

• In the Startup.cs class, create a private logger class variable:

private readonly ILogger<Startup> logger;

• In the Startup.cs constructor, add an ILoggerFactory parameter and create the logger:

public Startup(IHostingEnvironment env, ILoggerFactory loggerFactory)
{
	// logging was configured in Programs.cs, now it can be used here in Startup when the ILoggerFactory is a Startup constructor parameter
	logger = loggerFactory.CreateLogger<Startup>();
	...

• In the Configure method of Startup.cs, you can now remove the ILoggerFactory method parameter any lines you had to add Console and Debug logging:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
  // loggerFactory.AddConsole(Configuration.GetSection("Logging"));
  // loggerFactory.AddDebug();

• Logging is now available in Startup.cs! Give it a try:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
	logger.LogInformation("Hello from startup.cs!");
	...

---

How to also output to the nLog provider:

• Add the NLog.Extensions.Logging NuGet package
• Follow the instructions from the nLog NuGet site to add an nLog config file, add nLog from Startup.cs, and publish the nLog.config.

This repo demonstrates using nLog in conjunction with Console logging.

For more information on logging with .NET Core and a list of other supported logging providers, see the ASP.NET Core documentation on logging.