Console log output

Implement log output for console applications, supporting custom text/background colors per log level, which delivers great visibility during debugging.

1. Create a new Console Application in Visual Studio
2. Add the App.config configuration file to your project
3. Install log4net (via NuGet / reference log4net.dll)
4. Write log4net settings inside App.config
5. Initialize log4net in code and print logs

You can set foreground and background colors for different log levels in console logs to distinguish log types.

App.config Configuration

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
  </configSections>

  <log4net>
    <!-- Colored console output appender ColoredConsoleAppender -->
    <appender name="ColoredConsoleAppender" type="log4net.Appender.ColoredConsoleAppender">
      <!-- ERROR level color scheme -->
      <mapping>
        <level value="ERROR" />
        <foreColor value="White" />
        <backColor value="Red, HighIntensity" />
      </mapping>
      <!-- DEBUG level color scheme -->
      <mapping>
        <level value="DEBUG" />
        <backColor value="Green" />
      </mapping>
      <!-- INFO level color scheme -->
      <mapping>
        <level value="Info" />
        <backColor value="Yellow" />
      </mapping>
      <!-- Add custom mapping colors for WARN, FATAL as needed -->

      <!-- Log output format template -->
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
      </layout>
    </appender>

    <!-- Root logger, enable console output -->
    <root>
      <level value="All" />
      <appender-ref ref="ColoredConsoleAppender" />
    </root>
  </log4net>
</configuration>Code language: HTML, XML (xml)

Format Placeholder Explanation

• %date: Log timestamp
• [%thread]: Thread ID
• %-5level: Log level (aligned with 5‑character width)
• %logger: Class name of the logger
• %message: Log content body
• %newline: Automatic line break

Program.cs

using System;
using log4net;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            // Load and initialize log4net configuration
            log4net.Config.XmlConfigurator.Configure();
            // Get logger instance, pass in current class type for easier log source tracing
            ILog logger = LogManager.GetLogger(typeof(Program));

            // Output logs of all severity levels
            logger.Info("General log");
            logger.Error("Error log");
            logger.Debug("Debug message");
            logger.Fatal("Fatal error");
            logger.Warn("Warning message");

            Console.ReadKey();
        }
    }
}Code language: JavaScript (javascript)

Running Result

Different log levels render distinct background colors automatically in console:

• INFO: Yellow background
• DEBUG: Green background
• ERROR / FATAL: Bright red background
• WARN: Yellow background

Sample output:

2017-03-21 20:35:31,550 [9] INFO  ConsoleApplication1.Program [(null)] - General log
2017-03-21 20:35:31,592 [9] ERROR ConsoleApplication1.Program [(null)] - Error log
2017-03-21 20:35:31,592 [9] DEBUG ConsoleApplication1.Program [(null)] - Debug message
2017-03-21 20:35:31,593 [9] FATAL ConsoleApplication1.Program [(null)] - Fatal error
2017-03-21 20:35:31,594 [9] WARN  ConsoleApplication1.Program [(null)] - Warning messageCode language: CSS (css)

Console log output