Adding Log4Net Support

To integrate Log4Net into your ASP.NET Core application, install the Log4Net and Microsoft.Extensions.Logging.Log4Net.AspNetCore NuGet packages.

Setting Up Log4Net Configuration

Configuring the Log4Net Settings File

Create a configuration file named log4net.config with the following structure:

<?xml version="1.0" encoding="utf-8" ?>
<log4net>
    <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
      <file value="log\log.txt" />
      <appendToFile value="true" />
      <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
      <datePattern value="yyyyMMdd.txt" />
      <rollingStyle value="Size" />
      <maxSizeRollBackups value="-1" />
      <maximumFileSize value="50MB" />
      <layout type="log4net.Layout.PatternLayout">
          <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
    </appender>
    <root>
        <level value="ALL" />
        <appender-ref ref="RollingLogFileAppender" />
    </root>
</log4net>

Initializing Log4Net in Program.cs

In the Program.cs file, configure logging using the following setup:

public static IHostBuilder CreateHostBuilder(string[] args) =>
    Host.CreateDefaultBuilder(args)
        .ConfigureLogging(loggingBuilder =>
        {
            loggingBuilder.AddLog4Net("Config/log4net.config");
        })
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseStartup<Startup>();
        });

Implementing Logging in Controllers

Utilize dependency injection to access the logger within your controllers:

[ApiController]
[Route("api/[controller]")]
public class WeatherForecastController : ControllerBase
{
    private static readonly string[] Summaries = new[]
    {
        "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
    };

    private readonly ILogger<WeatherForecastController> _logger;

    public WeatherForecastController(ILogger<WeatherForecastController> logger)
    {
        _logger = logger;
    }

    [HttpGet]
    public IEnumerable<WeatherForecast> Get()
    {
        _logger.LogInformation("Fetching weather forecast data");

        var rng = new Random();
        return Enumerable.Range(1, 5).Select(index => new WeatherForecast
        {
            Date = DateTime.Now.AddDays(index),
            TemperatureC = rng.Next(-20, 55),
            Summary = Summaries[rng.Next(Summaries.Length)]
        })
        .ToArray();
    }
}

Filtering Default Logs

To suppress default system logs, apply filters in the logging builder:

loggingBuilder.AddFilter("System", LogLevel.Information);
loggingBuilder.AddFilter("System", LogLevel.Warning);
loggingBuilder.AddFilter("Microsoft", LogLevel.Information);
loggingBuilder.AddFilter("Microsoft", LogLevel.Warning);
loggingBuilder.AddFilter("Microsoft.Hosting.Lifetime", LogLevel.Information);
loggingBuilder.AddFilter("Microsoft.Hosting.Lifetime", LogLevel.Warning);