Logging to file in asp.net core using nlog

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In this video we will discuss how to log to a file in ASP.NET Core using NLog.

ASP.NET Core supports several third-party logging providers like the following

• NLog
• Serilog
• elmah
• Sentry
• JSNLog

If we know how to work with one of the third-party logging providers, working with the other's is similar.

Using NLog in ASP.NET Core

Step 1 : Install NLog.Web.AspNetCore nuget package

Once the NLog package is installed, you will see the PackageReference included in the .csproj file

<PackageReference Include="NLog.Web.AspNetCore" Version="4.8.2" />

Step 2 : Create nlog.config file

Create nlog.config file in the root of your project. I have included the minimum configuration required.

<?xml version="1.0" encoding="utf-8" ?>

<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"

      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

  <!-- the targets to write to -->

  <targets>

    <!-- write logs to file  -->

    <target name="allfile" xsi:type="File"

            fileName="c:\DemoLogs\nlog-all-${shortdate}.log"/>

  </targets>

  <!-- rules to map from logger name to target -->

  <rules>

    <!--All logs, including from Microsoft-->

    <logger name="*" minlevel="Trace" writeTo="allfile" />

  </rules>

</nlog>

To learn more about the nlog.config file please refer to the following github wiki page
https://github.com/NLog/NLog/wiki/Configuration-file

Step 3 : Enable copy to bin folder

Right click on nlog.config file in the Solution Explorer and select Properties. In the Properties window set 

Copy to Output Directory = Copy if newer

Step 4 : Enable NLog as one of the Logging Provider

In addition to using the default logging providers (i.e Console, Debug & EventSource), we also added NLog using the extension method AddNLog(). This method is in NLog.Extensions.Logging namespace.

public class Program

{

    public static void Main(string[] args)

    {

        CreateWebHostBuilder(args).Build().Run();

    }

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>

        WebHost.CreateDefaultBuilder(args)

        .ConfigureLogging((hostingContext, logging) =>

        {

            logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));

            logging.AddConsole();

            logging.AddDebug();

            logging.AddEventSourceLogger();

            // Enable NLog as one of the Logging Provider

            logging.AddNLog();

        })

        .UseStartup<Startup>();

}

If you want only NLog as the logging provider, clear all the logging providers and then add NLog.

public class Program

{

    public static void Main(string[] args)

    {

        CreateWebHostBuilder(args).Build().Run();

    }

    public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>

        WebHost.CreateDefaultBuilder(args)

        .ConfigureLogging((hostingContext, logging) =>

        {

            // Remove all the default logging providers

            logging.ClearProviders();

            logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));

            // Add NLog as the Logging Provider

            logging.AddNLog();

        })

       .UseStartup<Startup>();

}

Next video : Control what is logged using the LogLevel configuration setting.