How To Configure Log4net In .NET 7 API

After installation, we need to configure it with our project. The main part of the configuration starts from here. log4net is not a .NET library so it'll not be configured automatically, we need to configure it manually. Here we need a configuration file containing that information of configuration like where you want to store your log, the name of your log file, and the format of your file, etc. To do all these configurations we need a configuration file, let's move to our next step.

Step 7

Right-click on the project name and click on Add then click on New Item

Figure-adding new file

Then search for configuration and choose Web Configuration File and enter the file name then click on add button

Figure-adding configuration file

Now we need to add configuration settings in this file let's move toward to next step.

Step 8

Here we add this code

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
	<log4net>
		<appender name="RollingLogFileAppender"
				  type="log4net.Appender.RollingFileAppender">
			<lockingModel type="log4net.Appender.FileAppender+MinimalLock"/>
			<file value="location put here ie D:\TestLog\" />
			<datePattern value="yyyy-MM-dd.'txt'"/>
			<staticLogFileName value="false"/>
			<appendToFile value="true"/>
			<rollingStyle value="Date"/>
			<maxSizeRollBackups value="100"/>
			<maximumFileSize value="15MB"/>
			<layout type="log4net.Layout.PatternLayout">
				<conversionPattern
					value="%date [%thread] %-5level App  %newline %message %newline %newline"/>
			</layout>
		</appender>
		<root>
			<level value="INFO"/>
			<appender-ref ref="RollingLogFileAppender"/>
		</root>
	</log4net>
</configuration>

In this code, I have defined the setting related to logging like file-name, file-location, RollingLogFileAppender, etc that are required. You can also define the size of your file as I have defined 15 MB.

<maximumFileSize value="15MB"/> 

You can increase or decrease the file size depending on your requirement. Now most of the things are ready we just need to load these settings and use the logger.

Step 9

Now we need to load the .config file and log the exception and related information. I'm going to use the WeatherForecastController. I have created a method with the name private void LogError(string message) to load the .config file and log the error.

private  void LogError(string message)
{
    var logRepository = LogManager.GetRepository(Assembly.GetEntryAssembly());
    XmlConfigurator.Configure(logRepository, new FileInfo("log4net.config"));
    ILog _logger = LogManager.GetLogger(typeof(LoggerManager));
    _logger.Info(message);
}

Here you have to put the same name that you entered at the time of adding the configuration file

XmlConfigurator.Configure(logRepository, new FileInfo("log4net.config"));

like I have entered log4net.config. Now you just need to call this method and pass the exception. Here I have created an exception manually by adding a method private int div(int x). This method generates a divide by zero type exception

private int div(int x)
{
  return x / 0;
}

Now I have called this method under the try block and called that LogError method in the catch block, and it will log the exception

[HttpGet(Name = "GetWeatherForecast")]
public IEnumerable < WeatherForecast > Get() {
  try {
    int x = div(50);
    return Enumerable.Range(1, 5).Select(index =>new WeatherForecast {
      Date = DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
      TemperatureC = Random.Shared.Next( - 20, 55),
      Summary = Summaries[Random.Shared.Next(Summaries.Length)]

    }).ToArray();
  }
  catch(Exception ex) {
    LogError(ex.Message);
    throw;
  }
}

When we run the program and execute the following call we get an exception

Figure-Exception

Now if we check our log file then the log message would be written with the given format, let's have a look

Figure-Log information

Conclusion

In this article, we have created a log4net-configured API project. This one was a normal project structure if you want to use it on your product then I would suggest creating an Interface and defining logging methods there and then using them in your project after implementation.