NLog C# (Wie es für Entwickler funktioniert)

To create an NLog configuration file (typically named nlog.config), you can follow these steps. This configuration file will specify how NLog should behave in your application, including log targets, layout renderers, and rules.

In your project, right-click on the project or the desired folder where you want to create the configuration file.

1. Choose "Add" > "New Item..."
2. In the "Add New Item" dialog, search for "XML File" or "XML" and select it.

3. Name the file nlog.config and click the "Add" button.

   

4. Open the newly created nlog.config file in a text editor or XML editor.
5. Add the following configuration in the NLog.XML file. Below is a basic example of an NLog configuration that logs messages to a Console target. You can customize this Config File to suit your needs:

Config 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">

  <!-- Define targets -->
  <targets>
    <!-- Log to a console -->
    <target name="console" xsi:type="Console" layout="${longdate}|${message}"/>
  </targets>

  <!-- Define rules -->
  <rules>
    <!-- All messages with a minimum log level of Debug or higher are written to the Console -->
    <logger name="*" minlevel="Debug" writeTo="console" />
  </rules>

</nlog>

<?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">

  <!-- Define targets -->
  <targets>
    <!-- Log to a console -->
    <target name="console" xsi:type="Console" layout="${longdate}|${message}"/>
  </targets>

  <!-- Define rules -->
  <rules>
    <!-- All messages with a minimum log level of Debug or higher are written to the Console -->
    <logger name="*" minlevel="Debug" writeTo="console" />
  </rules>

</nlog>

In your C# code, make sure you load the NLog configuration from the nlog.config file. You typically do this in the application's startup code, such as in an ASP.NET Core Startup.cs(for .NET Version same or older than .NET 5), program.cs file (for .NET 6 or later version), or a console application's Main method:

using NLog;

internal class Program
{
    // Create an instance of the Logger
    private static Logger logger = LogManager.GetCurrentClassLogger();

    static void Main(string[] args)
    {
        // Log a debug message
        logger.Debug("This is a Debug Message");

        // Pause the console for viewing output
        Console.Read();
    }
}

using NLog;

internal class Program
{
    // Create an instance of the Logger
    private static Logger logger = LogManager.GetCurrentClassLogger();

    static void Main(string[] args)
    {
        // Log a debug message
        logger.Debug("This is a Debug Message");

        // Pause the console for viewing output
        Console.Read();
    }
}

Imports NLog

Friend Class Program
	' Create an instance of the Logger
	Private Shared logger As Logger = LogManager.GetCurrentClassLogger()

	Shared Sub Main(ByVal args() As String)
		' Log a debug message
		logger.Debug("This is a Debug Message")

		' Pause the console for viewing output
		Console.Read()
	End Sub
End Class

The output of the above program is as shown:

In this example, we create an instance of the Logger class and use it to log messages at the Debug Level. Let's explore the tracing level supported by NLog.

Logging Levels

NLog supports several logging levels, each with its own significance:

1. Trace: The most detailed level, typically used for diagnostic purposes.
2. Debug: Used for debugging information that can be helpful during development.
3. Info: General information about the application's operation.
4. Warn: Indicates a potential issue that does not disrupt the application.
5. Error: Indicates a failure that should be investigated but doesn't necessarily crash the application.
6. Fatal: Indicates a critical failure that should be addressed immediately.

By categorizing log messages into these levels, you can easily filter and prioritize them based on their severity.

Set minlevel="Trace" in the rules tag in your nLog.Config file as shown below.

<rules>
  <!-- All messages with a minimum log level of Trace or higher are written to the Console -->
  <logger name="*" minlevel="Trace" writeTo="console" />
</rules>

<rules>
  <!-- All messages with a minimum log level of Trace or higher are written to the Console -->
  <logger name="*" minlevel="Trace" writeTo="console" />
</rules>

Let's write code to log messages of all tracing levels.

using NLog;

internal class Program
{
    // Create an instance of the Logger
    private static Logger logger = LogManager.GetCurrentClassLogger();

    static void Main(string[] args)
    {
        // Log messages of different tracking levels
        logger.Trace("This is a Trace Message");
        logger.Debug("This is a Debug Message");
        logger.Info("This is an Info Message");
        logger.Warn("This is a Warning Message");
        logger.Error("This is an Error Message");
        logger.Fatal("This is a Fatal Message");

        // Pause the console for viewing output
        Console.Read();
    }
}

using NLog;

internal class Program
{
    // Create an instance of the Logger
    private static Logger logger = LogManager.GetCurrentClassLogger();

    static void Main(string[] args)
    {
        // Log messages of different tracking levels
        logger.Trace("This is a Trace Message");
        logger.Debug("This is a Debug Message");
        logger.Info("This is an Info Message");
        logger.Warn("This is a Warning Message");
        logger.Error("This is an Error Message");
        logger.Fatal("This is a Fatal Message");

        // Pause the console for viewing output
        Console.Read();
    }
}

Imports NLog

Friend Class Program
	' Create an instance of the Logger
	Private Shared logger As Logger = LogManager.GetCurrentClassLogger()

	Shared Sub Main(ByVal args() As String)
		' Log messages of different tracking levels
		logger.Trace("This is a Trace Message")
		logger.Debug("This is a Debug Message")
		logger.Info("This is an Info Message")
		logger.Warn("This is a Warning Message")
		logger.Error("This is an Error Message")
		logger.Fatal("This is a Fatal Message")

		' Pause the console for viewing output
		Console.Read()
	End Sub
End Class

Our Program has logged messages in the Console as shown below.

Now, We have demonstrated the example of logging messages in the Console. Now we will configure an NLog target to log messages in the file.

Log Message in File

We need to set a file target instead of a Console target in our config file for file logging.

<targets>
  <!-- Log to a file at specified location -->
  <target xsi:type="File" name="fileTarget" fileName="D:\Logs\mylog.txt" layout="${longdate} ${level:uppercase=true} ${message}" />
</targets>

<rules>
  <!-- All messages with a minimum log level of Trace or higher are written to the file -->
  <logger name="*" minlevel="Trace" writeTo="fileTarget" />
</rules>

<targets>
  <!-- Log to a file at specified location -->
  <target xsi:type="File" name="fileTarget" fileName="D:\Logs\mylog.txt" layout="${longdate} ${level:uppercase=true} ${message}" />
</targets>

<rules>
  <!-- All messages with a minimum log level of Trace or higher are written to the file -->
  <logger name="*" minlevel="Trace" writeTo="fileTarget" />
</rules>

Now, run the program to log messages in a file.

Logging targets

NLog supports various log output targets, allowing you to choose where your log messages should be stored. Some common targets include:

1. File: Logs messages to one or more files.
2. Console: Logs messages to the console.
3. Database: Logs messages to a database (SQL Server, MySQL, Oracle, PostgreSQL, etc.) table.
4. Email: Sends log messages as emails.
5. Event Log: Logs messages to the Windows Event Log.
6. Custom Targets: You can create custom log targets to fit your specific needs.

You can configure NLog to use one or more targets simultaneously.

PDF Generation with Logging

Install-Package IronPdf

using NLog;
using IronPdf;

internal class Program
{
    // Create an instance of the Logger
    private static Logger logger = LogManager.GetCurrentClassLogger();

    static void Main(string[] args)
    {
        logger.Info("Initializing Chrome PDF Renderer");
        ChromePdfRenderer renderer = new ChromePdfRenderer();

        logger.Info("Creating PDF From HTML String");
        var pdf = renderer.RenderHtmlAsPdf("<h1>This is my Sample PDF<h1>");

        logger.Info("Saving PDF File");
        pdf.SaveAs(@"D:\myPDF.pdf");
    }
}

using NLog;
using IronPdf;

internal class Program
{
    // Create an instance of the Logger
    private static Logger logger = LogManager.GetCurrentClassLogger();

    static void Main(string[] args)
    {
        logger.Info("Initializing Chrome PDF Renderer");
        ChromePdfRenderer renderer = new ChromePdfRenderer();

        logger.Info("Creating PDF From HTML String");
        var pdf = renderer.RenderHtmlAsPdf("<h1>This is my Sample PDF<h1>");

        logger.Info("Saving PDF File");
        pdf.SaveAs(@"D:\myPDF.pdf");
    }
}

Imports NLog
Imports IronPdf

Friend Class Program
	' Create an instance of the Logger
	Private Shared logger As Logger = LogManager.GetCurrentClassLogger()

	Shared Sub Main(ByVal args() As String)
		logger.Info("Initializing Chrome PDF Renderer")
		Dim renderer As New ChromePdfRenderer()

		logger.Info("Creating PDF From HTML String")
		Dim pdf = renderer.RenderHtmlAsPdf("<h1>This is my Sample PDF<h1>")

		logger.Info("Saving PDF File")
		pdf.SaveAs("D:\myPDF.pdf")
	End Sub
End Class