Logging in .NET Core without DI?

user_178757 0
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It seems that Microsoft are really trying to shove DI down your throat with .NET Core, and I'm not sure why, but frankly my console app is small and simple and I just don't want to build a whole DI container just to do some simple logging. How can I do logging in .NET Core without using DI? Everything I've read assumed you're going to use .NET Core's built-in logging architecture which obviously requires DI, but there must be a way to just do it without DI using a static variable on the class?

asp.net-core logging c#
4 Answers

If you want to do it yourself you will need to instantiate a LoggerFactory instance somewhere and configure what providers you want. Then you just need to call CreateLogger to create a instance or use new Logger<T>(ILoggerFactory) to create a logger.

using Microsoft.Extensions.Logging;

static class MyLogger {

    public static ILoggerFactory LoggerFactory {get;}

    static MyLogger() {
        LoggerFactory = new LoggerFactory();
        LoggerFactory.AddConsole();
    }
}

public MyClass {
    private readonly ILogger _logger = new Logger<MyClass>(MyLogger.LoggerFactory);
}
user_802740

As per Ilyas and bokibegs comments in Scotts answer here is the currently working code for .NET 5.0

using Microsoft.Extensions.Logging
var factory = LoggerFactory.Create(b => b.AddConsole());
var logger = factory.CreateLogger<T>();

This requires the Microsoft.Extensions.Logging and Microsoft.Extensions.Logging.Console nuget packages.

user_20506370

What I ended up doing was using NLog but rather than using their .NET Core DI extensions, I just included the main NLog NuGet package, manually creating my own NLog.config file, and followed the tutorial to GetCurrentClassLogger(), creating that as a static member of my class, then directly used that for logging. This is quite a simple setup and has no need for DI. NLog should probably document it better.

user_1787570

Complete example using .NET Core 6 and NLog 4.7.

  1. Run dotnet new console
  2. Run dotnet add package NLog
  3. Create a new text file named NLog.config1.
<?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">

    <targets>
        <target name="logfile" xsi:type="File" fileName="file.txt" />
        <target name="logconsole" xsi:type="Console" />
    </targets>

    <rules>
        <logger name="*" minlevel="Info" writeTo="logconsole" />
        <logger name="*" minlevel="Debug" writeTo="logfile" />
    </rules>
</nlog>
  1. Add the NLog.config file to your project file.
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <None Include="NLog.config">
      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
    </None>
  </ItemGroup>

  <ItemGroup>
    <PackageReference Include="NLog" Version="4.7.13" />
  </ItemGroup>
</Project>
  1. Edit the Program.cs file as follows:
var logger = NLog.LogManager.GetCurrentClassLogger();
logger.Info("Program started.");
logger.Info("Program completed.");
  1. Run dotnet run.

Expected Output

> dotnet run
2022-02-08 17:23:37.0430|INFO|Program|Program started.
2022-02-08 17:23:37.0924|INFO|Program|Program completed.

1https://github.com/NLog/NLog/wiki/Tutorial#configure-nlog-targets-for-output

user_1679200
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