ASP.NET Core: NLog

Introduction

In this article, we will learn how to archive log files using NLog with ASP.NET Core .Most of the time, we will store logs in files, and we should archive them so that we can manage them easier. Let's take a look at how to use NLog to archive log files.

Steps To Be Followed

Step 1: New Application

Create a new ASP.NET Core Web API Application and install NLog.Web.AspNetCore via nuget.

Install-Package NLog.Web.AspNetCore

Step 2: nlog.config

Create a nlog.config file, and enable copy to bin folder.

We just archive the log files via this configuration file.

<?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"> 
  
 <!-- the targets to write to --> 
 <targets> 
    
  <target xsi:type="File" 
    name="archive" 
    archiveEvery="Day" 
    archiveFileName = "nlogdemo-{########}.log" 
    archiveNumbering = "Date" 
    archiveDateFormat = "yyyyMMdd" 
    maxArchiveFiles = "4" 
    fileName="nlogdemo.log" 
    layout="${longdate}|${level:uppercase=true}|${logger}|${message}" /> 
            
  </targets> 
  
 <!-- rules to map from logger name to target --> 
 <rules> 
  <!--All logs, including from Microsoft--> 
  <logger name="*" minlevel="Warn" writeTo="archive" /> 
 </rules> 
</nlog> 

Just pay attention to the options that contains archive.

The above configuration means that we have a main log file named nlogdemo.log which stores today's log.

It will archive logs daily and the file name of the archive log file will be formatted like nlogdemo-20180505.log.

And the max number of archived log files is 4 which means it will keep only the newest 4 files.

Step 3: program.cs

Update program.cs so that we can enable NLog. 

namespace NLogDemo 
{ 
  using Microsoft.AspNetCore; 
  using Microsoft.AspNetCore.Hosting; 
  using NLog.Web; 
  
  public class Program 
  { 
    public static void Main(string[] args) 
    { 
      BuildWebHost(args).Run(); 
    } 
  
    public static IWebHost BuildWebHost(string[] args) => 
      WebHost.CreateDefaultBuilder(args) 
        .UseStartup<Startup>() 
        .UseNLog() 
        .Build(); 
  } 
} 

Step 4

Write some logs in controller. 

private readonly ILogger _logger; 
  
public ValuesController(ILoggerFactory loggerFactory) 
{ 
  _logger = loggerFactory.CreateLogger<ValuesController>(); 
} 
  
// GET api/values 
[HttpGet] 
public IEnumerable<string> Get() 
{ 
  _logger.LogDebug("debug"); 
  _logger.LogError("error"); 
  _logger.LogTrace("trace"); 
  _logger.LogInformation("info"); 
  _logger.LogWarning("warn"); 
  _logger.LogCritical("critical"); 
  
  return new string[] { "value1", "value2" }; 
} 

Now, change the date of computer then we can see log file with updated date.

Summary

• Basic configuration to archive log files using NLog.