Getting started with ASP.NET Core 3

⚠️ Missing the trace/debug logs? Check your appsettings.json

ℹ️ See also example in GitHub

This tutorial is for ASP.NET Core 3.1

For ASP.NET Core 6, check Getting started with ASP.NET Core 6

0. Create a new ASP.NET Core project

In Visual Studio 2019.

1. Add dependency in csproj manually or using NuGet

Install the latest:

NLog.Web.AspNetCore 4.9+
Update the NLog package if possible

in csproj:

<PackageReference Include="NLog.Web.AspNetCore" Version="4.*" />
<PackageReference Include="NLog" Version="4.*" />

2. Create a nlog.config file.

Create nlog.config (lowercase all) file in the root of your project.

We use this example:

<?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"
      autoReload="true"
      throwConfigExceptions="true"
      internalLogLevel="info"
      internalLogFile="c:\temp\internal-nlog-AspNetCore3.txt">

  <!-- enable asp.net core layout renderers -->
  <extensions>
    <add assembly="NLog.Web.AspNetCore"/>
  </extensions>

  <!-- the targets to write to -->
  <targets>
    <!-- File Target for all log messages with basic details -->
    <target xsi:type="File" name="allfile" fileName="c:\temp\nlog-AspNetCore3-all-${shortdate}.log"
            layout="${longdate}|${event-properties:item=EventId_Id:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}" />

    <!-- File Target for own log messages with extra web details using some ASP.NET core renderers -->
    <target xsi:type="File" name="ownFile-web" fileName="c:\temp\nlog-AspNetCore3-own-${shortdate}.log"
            layout="${longdate}|${event-properties:item=EventId_Id:whenEmpty=0}|${level:uppercase=true}|${logger}|${message} ${exception:format=tostring}|url: ${aspnet-request-url}|action: ${aspnet-mvc-action}|" />

    <!--Console Target for hosting lifetime messages to improve Docker / Visual Studio startup detection -->
    <target xsi:type="Console" name="lifetimeConsole" layout="${MicrosoftConsoleLayout}" />
  </targets>

  <!-- rules to map from logger name to target -->
  <rules>
    <!--All logs, including from Microsoft-->
    <logger name="*" minlevel="Trace" writeTo="allfile" />

    <!--Output hosting lifetime messages to console target for faster startup detection -->
    <logger name="Microsoft.Hosting.Lifetime" minlevel="Info" writeTo="lifetimeConsole, ownFile-web" final="true" />

    <!--Skip non-critical Microsoft logs and so log only own logs-->
    <logger name="Microsoft.*" maxlevel="Info" final="true" />  <!-- BlackHole -->

    <logger name="*" minlevel="Trace" writeTo="ownFile-web" />
  </rules>
</nlog>

More details of the config file are here.

Notice that one might have to pay special attention to the Hosting Lifetime Startup Messages, if removing all other LoggingProviders (Like Console) and only using NLog. As it can cause hosting environment (Visual Studio / Docker / Azure Container) to not see application as started.

If you like to include other targets or layout renderers, check the Platform support table, as there is a limited set implemented. Check the column NetStandard. To read more about NetStandard, see the docs from Microsoft. Check .NET Standard 2 for ASP.NET Core 3.

3. Enable copy to bin folder

Enable copy to bin folder for nlog.config

NLogConfig

or edit .csproj file manually and add:

  <ItemGroup>
    <Content Update="nlog.config" CopyToOutputDirectory="PreserveNewest" />
  </ItemGroup>

4. Update program.cs

Update the program.cs

using System;
using NLog.Web;
using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Hosting;

public static void Main(string[] args)
{
    var logger = NLog.LogManager.Setup().LoadConfigurationFromAppSettings().GetCurrentClassLogger();

    try
    {
        logger.Debug("init main");
        CreateHostBuilder(args).Build().Run();
    }
    catch (Exception exception)
    {
        //NLog: catch setup errors
        logger.Error(exception, "Stopped program because of exception");
        throw;
    }
    finally
    {
        // Ensure to flush and stop internal timers/threads before application-exit (Avoid segmentation fault on Linux)
        NLog.LogManager.Shutdown();
    }
}

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseStartup<Startup>();
        })
        .ConfigureLogging(logging =>
        {
            logging.ClearProviders();
            logging.SetMinimumLevel(Microsoft.Extensions.Logging.LogLevel.Trace);
        })
        .UseNLog();  // NLog: Setup NLog for Dependency injection

5. Configure appsettings.json

The Logging configuration specified in appsettings.json overrides any call to SetMinimumLevel. So either remove "Default": or adjust it correctly to your needs.

{
  "Logging": {
    "LogLevel": {
      "Default": "Trace",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*"
}

Remember to also update any environment specific configuration to avoid any surprises. Ex appsettings.Development.json

6. Write logs

Inject the ILogger in your controller:

using Microsoft.Extensions.Logging;

public class HomeController : Controller
{
    private readonly ILogger<HomeController> _logger;

    public HomeController(ILogger<HomeController> logger)
    {
        _logger = logger;
        _logger.LogDebug(1, "NLog injected into HomeController");
    }

    public IActionResult Index()
    {
        _logger.LogInformation("Hello, this is the index!");
        return View();
    }

7. Example Output

When starting the ASP.NET Core website, we get two files:

nlog-own-2019-10-14.log

2019-10-14 23:15:09.3898|0|DEBUG|ASP.NET_Core_3___VS2019.Program|init main |url: |action: |ASP.NET_Core_3___VS2019.Program.Main
2019-10-14 23:15:11.3867|1|DEBUG|ASP.NET_Core_3___VS2019.Controllers.HomeController|NLog injected into HomeController |url: https://localhost/|action: Index|ASP.NET_Core_3___VS2019.Controllers.HomeController..ctor
2019-10-14 23:15:11.3867|0|INFO|ASP.NET_Core_3___VS2019.Controllers.HomeController|Hello, this is the index! |url: https://localhost/|action: Index|ASP.NET_Core_3___VS2019.Controllers.HomeController.Index

nlog-all-2019-10-14.log

2019-10-14 23:15:09.3898|0|DEBUG|ASP.NET_Core_3___VS2019.Program|init main 
2019-10-14 23:15:10.9142|0|INFO|Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager|User profile is available. Using 'C:\Users\Julian\AppData\Local\ASP.NET\DataProtection-Keys' as key repository and Windows DPAPI to encrypt keys at rest. 
2019-10-14 23:15:11.2680|0|INFO|Microsoft.Hosting.Lifetime|Application started. Press Ctrl+C to shut down. 
2019-10-14 23:15:11.2680|0|INFO|Microsoft.Hosting.Lifetime|Hosting environment: Development 
2019-10-14 23:15:11.2680|0|INFO|Microsoft.Hosting.Lifetime|Content root path: D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019 
2019-10-14 23:15:11.3238|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/   
2019-10-14 23:15:11.3434|0|INFO|Microsoft.AspNetCore.Routing.EndpointMiddleware|Executing endpoint 'ASP.NET_Core_3___VS2019.Controllers.HomeController.Index (ASP.NET Core 3 - VS2019)' 
2019-10-14 23:15:11.3867|3|INFO|Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker|Route matched with {action = "Index", controller = "Home"}. Executing controller action with signature Microsoft.AspNetCore.Mvc.IActionResult Index() on controller ASP.NET_Core_3___VS2019.Controllers.HomeController (ASP.NET Core 3 - VS2019). 
2019-10-14 23:15:11.3867|1|DEBUG|ASP.NET_Core_3___VS2019.Controllers.HomeController|NLog injected into HomeController 
2019-10-14 23:15:11.3867|0|INFO|ASP.NET_Core_3___VS2019.Controllers.HomeController|Hello, this is the index! 
2019-10-14 23:15:11.4161|1|INFO|Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor|Executing ViewResult, running view Index. 
2019-10-14 23:15:11.5831|4|INFO|Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor|Executed ViewResult - view Index executed in 167.626ms. 
2019-10-14 23:15:11.5831|2|INFO|Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker|Executed action ASP.NET_Core_3___VS2019.Controllers.HomeController.Index (ASP.NET Core 3 - VS2019) in 196.6052ms 
2019-10-14 23:15:11.5831|1|INFO|Microsoft.AspNetCore.Routing.EndpointMiddleware|Executed endpoint 'ASP.NET_Core_3___VS2019.Controllers.HomeController.Index (ASP.NET Core 3 - VS2019)' 
2019-10-14 23:15:11.5910|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 267.9366ms 200 text/html; charset=utf-8 
2019-10-14 23:15:11.6171|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/lib/jquery/dist/jquery.min.js   
2019-10-14 23:15:11.6171|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/css/site.css   
2019-10-14 23:15:11.6171|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/lib/bootstrap/dist/css/bootstrap.min.css   
2019-10-14 23:15:11.6365|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/lib/bootstrap/dist/js/bootstrap.bundle.min.js   
2019-10-14 23:15:11.6365|1|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request starting HTTP/2.0 GET https://localhost:44318/js/site.js?v=4q1jwFhaPaZgr8WAUSrux6hAuh0XDg9kPS3xIVq36I0   
2019-10-14 23:15:11.6627|2|INFO|Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware|Sending file. Request path: '/js/site.js'. Physical path: 'D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019\wwwroot\js\site.js' 
2019-10-14 23:15:11.6627|2|INFO|Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware|Sending file. Request path: '/css/site.css'. Physical path: 'D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019\wwwroot\css\site.css' 
2019-10-14 23:15:11.6627|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 28.7787ms 200 application/javascript 
2019-10-14 23:15:11.6696|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 52.4825ms 200 text/css 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware|Sending file. Request path: '/lib/bootstrap/dist/js/bootstrap.bundle.min.js'. Physical path: 'D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019\wwwroot\lib\bootstrap\dist\js\bootstrap.bundle.min.js' 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware|Sending file. Request path: '/lib/bootstrap/dist/css/bootstrap.min.css'. Physical path: 'D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019\wwwroot\lib\bootstrap\dist\css\bootstrap.min.css' 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware|Sending file. Request path: '/lib/jquery/dist/jquery.min.js'. Physical path: 'D:\nlog\NLog.Web\examples\ASP.NET Core 3\ASP.NET Core 3 - VS2019\wwwroot\lib\jquery\dist\jquery.min.js' 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 50.937400000000004ms 200 application/javascript 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 70.65100000000001ms 200 text/css 
2019-10-14 23:15:11.6853|2|INFO|Microsoft.AspNetCore.Hosting.Diagnostics|Request finished in 71.51610000000001ms 200 application/javascript

Configure NLog Targets for output

Next step, see Configure NLog with nlog.config

- Troubleshooting Guide - See available NLog Targets and Layouts: https://nlog-project.org/config

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Getting started with ASP.NET Core 3

0. Create a new ASP.NET Core project

1. Add dependency in csproj manually or using NuGet

2. Create a nlog.config file.

3. Enable copy to bin folder

4. Update program.cs

5. Configure appsettings.json

6. Write logs

7. Example Output

nlog-own-2019-10-14.log

nlog-all-2019-10-14.log

Configure NLog Targets for output

Home

Configuration

Programmatic Configuration

Advanced

Extending NLog

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