ZidUtilities.CommonCode.Log4Net 1.0.1

CommonCode.Log4Net

Log4Net configuration helper library for programmatically generating log4net XML configuration files with support for console, rolling file, and JSON appenders.

Features

• Programmatic Configuration: Generate log4net XML configuration files using C# code instead of manual XML editing
• Multiple Appender Types: Support for Console, Rolling File, and JSON appenders
• Automatic JSON Member Generation: Convert pattern layouts to JSON members automatically
• Type-Safe Configuration: Strongly-typed classes for all configuration elements
• Easy Integration: Generate config files and load them with standard log4net API

Core Components

Log4NetConfigHelper

Main helper class for building and saving log4net configuration files.

Properties:

• RootLevel - Root logging level (ALL, DEBUG, INFO, WARN, ERROR, FATAL, OFF)
• Appenders - List of IAppender objects to include in configuration

Methods:

• SaveConfigToFile(string filePath) - Generates and saves the XML configuration file
• GetConfigXmlString(List<string> appenderNames) - Returns the XML configuration as a string

Appender Classes

ConsoleAppender - Colored console output

• Static method: GetDefault() - Returns pre-configured console appender
• Static method: DefaultMappings() - Returns default color mappings for log levels
• Static method: DefaultLayout() - Returns default pattern layout

RollingFileAppender - File logging with rolling capabilities

• Properties: FilePath, AppendToFile, RollingStyle, MaxFileSize, MaxSizeRollBackups, DatePattern
• Static method: GetDefault() - Returns pre-configured file appender
• Static method: DefaultLayout() - Returns default pattern layout

JsonFileAppender - JSON-formatted file logging

• Properties: FilePath, AppendToFile, RollingStyle, DatePattern, Members
• Static method: GetDefault() - Returns pre-configured JSON appender
• Static method: GetDefaultJsonMembers() - Returns default JSON member list
• Static method: GetMembersFromPattern(string pattern) - Converts pattern layout to JSON members

Supporting Classes

Log4NetLayout - Layout configuration for text-based appenders

• Type - Layout type (e.g., "log4net.Layout.PatternLayout")
• ConversionPattern - Pattern string for formatting log messages

Log4NetJsonMember - JSON member configuration

• Name - Member name in JSON output
• Value - Value pattern (can be log4net pattern tokens or literal values)

Log4NetMapping - Color mapping for console appender

• Level - Log level (DEBUG, INFO, WARN, ERROR, FATAL)
• ForeColor - Foreground color
• BackColor - Background color

Dependencies

• log4net (NuGet package)
• log4net.Ext.Json (for JSON appender support)

Target Framework

.NET Framework 4.8

Installation

1. Install log4net NuGet package:

   Install-Package log4net
   

2. For JSON logging support, install:

   Install-Package log4net.Ext.Json
   

3. Add reference to CommonCode.Log4Net.dll in your project

Usage Examples

Basic Console Appender Configuration

using log4net;
using log4net.Config;
using ZidUtilities.CommonCode.Log4Net;

// Create configuration helper
Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";

// Add console appender using defaults
config.Appenders.Add(ConsoleAppender.GetDefault());

// Save configuration to file
config.SaveConfigToFile("log4net.config");

// Load configuration into log4net
XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));

// Get logger and start logging
ILog log = LogManager.GetLogger(typeof(Program));
log.Debug("This is a debug message");
log.Info("This is an info message");
log.Warn("This is a warning message");
log.Error("This is an error message");
log.Fatal("This is a fatal message");

Rolling File Appender with Custom Settings

using log4net;
using log4net.Config;
using ZidUtilities.CommonCode.Log4Net;

Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";

// Create rolling file appender
RollingFileAppender rollingFileAppender = new RollingFileAppender()
{
    Name = "RollingFileAppender",
    LoggingLevel = "ALL",
    FilePath = "logs/application.log",
    AppendToFile = true,
    RollingStyle = "Date",        // Date-based rolling
    DatePattern = "yyyyMMdd",      // Creates new file each day
    Layout = new Log4NetLayout
    {
        Type = "log4net.Layout.PatternLayout",
        ConversionPattern = "[%date] [%thread] [%-5level] %message%newline%exception"
    }
};

config.Appenders.Add(rollingFileAppender);

// Save and load configuration
config.SaveConfigToFile("log4net.config");
XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));

// Use logger
ILog log = LogManager.GetLogger("MyApp");
log.Info("Application started");

Size-Based Rolling File Appender

Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";

// Size-based rolling
RollingFileAppender sizeRollingAppender = new RollingFileAppender()
{
    Name = "SizeRollingAppender",
    LoggingLevel = "ALL",
    FilePath = "logs/app.log",
    AppendToFile = true,
    RollingStyle = "Size",
    MaxFileSize = "10MB",
    MaxSizeRollBackups = 5,        // Keep 5 backup files
    Layout = RollingFileAppender.DefaultLayout()
};

config.Appenders.Add(sizeRollingAppender);
config.SaveConfigToFile("log4net.config");
XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));

JSON File Appender

using log4net;
using log4net.Config;
using ZidUtilities.CommonCode.Log4Net;
using System.Collections.Generic;

Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";

// Create JSON appender
JsonFileAppender jsonAppender = new JsonFileAppender()
{
    Name = "JsonFileAppender",
    LoggingLevel = "ALL",
    FilePath = "logs/application.json",
    AppendToFile = true,
    RollingStyle = "Date",
    DatePattern = "yyyyMMdd",
    Members = JsonFileAppender.GetDefaultJsonMembers()
};

config.Appenders.Add(jsonAppender);

// Save and load configuration

//FROM FILE
config.SaveConfigToFile("log4net.config");
XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));

//OR
//FROM STREAM
//XmlConfigurator.Configure(l4Config.GetConfigXmlStream());

ILog log = LogManager.GetLogger("MyApp");
log.Info("User logged in");
log.Error("Payment failed", new Exception("Insufficient funds"));

// JSON output format:
// {"date":"2024-01-15 10:30:45","level":"INFO","logger":"MyApp","message":"User logged in","exception":""}
// {"date":"2024-01-15 10:30:46","level":"ERROR","logger":"MyApp","message":"Payment failed","exception":"System.Exception: Insufficient funds..."}

JSON Appender with Custom Members

Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";

// Define custom JSON structure
List<Log4NetJsonMember> customMembers = new List<Log4NetJsonMember>
{
    new Log4NetJsonMember { Name = "timestamp", Value = "date" },
    new Log4NetJsonMember { Name = "severity", Value = "level" },
    new Log4NetJsonMember { Name = "source", Value = "logger" },
    new Log4NetJsonMember { Name = "text", Value = "messageObject" },
    new Log4NetJsonMember { Name = "error", Value = "exception" },
    new Log4NetJsonMember { Name = "thread_id", Value = "thread" },
    new Log4NetJsonMember { Name = "user", Value = "username" }
};

JsonFileAppender jsonAppender = new JsonFileAppender()
{
    Name = "CustomJsonAppender",
    LoggingLevel = "ALL",
    FilePath = "logs/custom.json",
    AppendToFile = true,
    RollingStyle = "Date",
    DatePattern = "yyyyMMdd",
    Members = customMembers
};

config.Appenders.Add(jsonAppender);
XmlConfigurator.Configure(config.GetConfigXmlStream());

Auto-Generate JSON Members from Pattern

The JsonFileAppender.GetMembersFromPattern() method automatically converts a pattern layout string into JSON members:

Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";

// Define your desired pattern
string pattern = "%date [%thread] [%username] [%identity] %level [%location] [%file] [%line] [%class] [%method] %logger - %message%newline%exception";

// Automatically convert pattern to JSON members
JsonFileAppender jsonAppender = new JsonFileAppender()
{
    Name = "AutoJsonAppender",
    LoggingLevel = "ALL",
    FilePath = "logs/auto.json",
    AppendToFile = true,
    RollingStyle = "Date",
    DatePattern = "yyyyMMdd",
    Members = JsonFileAppender.GetMembersFromPattern(pattern)
};

config.Appenders.Add(jsonAppender);
config.SaveConfigToFile("log4net.config");
XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));

// The generated JSON will include all fields from the pattern:
// date, thread, username, identity, level, location, file, line, class, method, logger, message, exception

Multiple Appenders Configuration

using log4net;
using log4net.Config;
using ZidUtilities.CommonCode.Log4Net;

Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";

// 1. Console appender for immediate feedback
config.Appenders.Add(ConsoleAppender.GetDefault());

// 2. Rolling file appender for text logs
RollingFileAppender textAppender = new RollingFileAppender()
{
    Name = "TextFileAppender",
    LoggingLevel = "ALL",
    FilePath = "logs/app.log",
    AppendToFile = true,
    RollingStyle = "Date",
    DatePattern = "yyyyMMdd",
    Layout = new Log4NetLayout
    {
        Type = "log4net.Layout.PatternLayout",
        ConversionPattern = "[%date] [%thread] [%-5level] %logger - %message%newline%exception"
    }
};
config.Appenders.Add(textAppender);

// 3. JSON appender for structured logging
string jsonPattern = "%date [%thread] %level %logger - %message%exception";
JsonFileAppender jsonAppender = new JsonFileAppender()
{
    Name = "JsonFileAppender",
    LoggingLevel = "ALL",
    FilePath = "logs/app.json",
    AppendToFile = true,
    RollingStyle = "Date",
    DatePattern = "yyyyMMdd",
    Members = JsonFileAppender.GetMembersFromPattern(jsonPattern)
};
config.Appenders.Add(jsonAppender);

//load configuration
XmlConfigurator.Configure(config.GetConfigXmlStream());

// All appenders will receive log messages
ILog log = LogManager.GetLogger("MyApp");
log.Info("This message goes to console, text file, and JSON file");

Custom Console Appender Colors

using ZidUtilities.CommonCode.Log4Net;
using System.Collections.Generic;

Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";

// Create custom color mappings
List<Log4NetMapping> customColors = new List<Log4NetMapping>
{
    new Log4NetMapping { Level = "DEBUG", ForeColor = "Cyan", BackColor = "Black" },
    new Log4NetMapping { Level = "INFO", ForeColor = "Green, HighIntensity", BackColor = "Black" },
    new Log4NetMapping { Level = "WARN", ForeColor = "Yellow, HighIntensity", BackColor = "Black" },
    new Log4NetMapping { Level = "ERROR", ForeColor = "Red, HighIntensity", BackColor = "Black" },
    new Log4NetMapping { Level = "FATAL", ForeColor = "White, HighIntensity", BackColor = "Red" }
};

ConsoleAppender consoleAppender = new ConsoleAppender
{
    Name = "CustomConsoleAppender",
    LoggingLevel = "ALL",
    Mappings = customColors,
    Layout = new Log4NetLayout
    {
        Type = "log4net.Layout.PatternLayout",
        ConversionPattern = "[%date{HH:mm:ss}] [%-5level] %message%newline"
    }
};

config.Appenders.Add(consoleAppender);
config.SaveConfigToFile("log4net.config");
XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));

Complete Application Example

using System;
using log4net;
using log4net.Config;
using ZidUtilities.CommonCode.Log4Net;

public class Program
{
    private static readonly ILog log = LogManager.GetLogger(typeof(Program));

    static void Main(string[] args)
    {
        // Configure logging first
        ConfigureLogging();

        log.Info("Application started");

        try
        {
            // Your application logic
            DoWork();

            log.Info("Application completed successfully");
        }
        catch (Exception ex)
        {
            log.Fatal("Application crashed", ex);
            throw;
        }
    }

    private static void ConfigureLogging()
    {
        Log4NetConfigHelper config = new Log4NetConfigHelper();
        config.RootLevel = "ALL";

        // Console appender
        config.Appenders.Add(ConsoleAppender.GetDefault());

        // Rolling file appender
        RollingFileAppender fileAppender = new RollingFileAppender()
        {
            Name = "RollingFileAppender",
            LoggingLevel = "ALL",
            FilePath = "logs/application.log",
            AppendToFile = true,
            RollingStyle = "Date",
            DatePattern = "yyyyMMdd",
            Layout = new Log4NetLayout
            {
                Type = "log4net.Layout.PatternLayout",
                ConversionPattern = "[%date] [%thread] [%-5level] %logger - %message%newline%exception"
            }
        };
        config.Appenders.Add(fileAppender);

        // JSON appender
        JsonFileAppender jsonAppender = new JsonFileAppender()
        {
            Name = "JsonFileAppender",
            LoggingLevel = "ALL",
            FilePath = "logs/application.json",
            AppendToFile = true,
            RollingStyle = "Date",
            DatePattern = "yyyyMMdd",
            Members = JsonFileAppender.GetDefaultJsonMembers()
        };
        config.Appenders.Add(jsonAppender);

        // Save configuration and load it
        config.SaveConfigToFile("log4net.config");
        XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));
    }

    private static void DoWork()
    {
        log.Debug("Starting work process");

        for (int i = 0; i < 10; i++)
        {
            log.InfoFormat("Processing item {0} of {1}", i + 1, 10);

            try
            {
                ProcessItem(i);
            }
            catch (Exception ex)
            {
                log.ErrorFormat("Error processing item {0}: {1}", i, ex.Message);
            }
        }

        log.Debug("Work process completed");
    }

    private static void ProcessItem(int itemId)
    {
        if (itemId == 5)
        {
            log.Warn("Item 5 requires special handling");
        }

        // Simulate work
        System.Threading.Thread.Sleep(100);

        if (itemId == 7)
        {
            throw new InvalidOperationException("Item 7 processing failed");
        }
    }
}

Different Logging Levels Example

Log4NetConfigHelper config = new Log4NetConfigHelper();

// Set root level to INFO - DEBUG messages won't be logged
config.RootLevel = "INFO";

config.Appenders.Add(ConsoleAppender.GetDefault());
config.SaveConfigToFile("log4net.config");
XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));

ILog log = LogManager.GetLogger("MyApp");

log.Debug("This will NOT be logged");        // Below INFO level
log.Info("This will be logged");             // INFO level
log.Warn("This will be logged");             // WARN level
log.Error("This will be logged");            // ERROR level
log.Fatal("This will be logged");            // FATAL level

// Root levels: ALL < DEBUG < INFO < WARN < ERROR < FATAL < OFF

Separate Appenders for Different Log Levels

Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";

// General log - all levels
RollingFileAppender generalLog = new RollingFileAppender()
{
    Name = "GeneralLog",
    LoggingLevel = "ALL",
    FilePath = "logs/general.log",
    AppendToFile = true,
    RollingStyle = "Date",
    DatePattern = "yyyyMMdd",
    Layout = RollingFileAppender.DefaultLayout()
};
config.Appenders.Add(generalLog);

// Error log - only errors and fatal
RollingFileAppender errorLog = new RollingFileAppender()
{
    Name = "ErrorLog",
    LoggingLevel = "ERROR",       // Only ERROR and FATAL
    FilePath = "logs/errors.log",
    AppendToFile = true,
    RollingStyle = "Date",
    DatePattern = "yyyyMMdd",
    Layout = new Log4NetLayout
    {
        Type = "log4net.Layout.PatternLayout",
        ConversionPattern = "[%date] [%-5level] %logger - %message%newline%exception"
    }
};
config.Appenders.Add(errorLog);

config.SaveConfigToFile("log4net.config");
XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));

ILog log = LogManager.GetLogger("MyApp");
log.Info("This goes only to general.log");
log.Error("This goes to both general.log and errors.log");

Dynamic Pattern Configuration

Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";

// Build pattern based on requirements
string pattern = "%date";

bool includeThread = true;
bool includeUsername = false;
bool includeLevel = true;
bool includeLogger = true;
bool includeLocation = false;

if (includeThread)
    pattern += " [%thread]";

if (includeUsername)
    pattern += " [%username]";

if (includeLevel)
    pattern += " [%-5level]";

if (includeLogger)
    pattern += " %logger";

if (includeLocation)
    pattern += " [%location]";

pattern += " - %message%newline%exception";

// Apply to rolling file
RollingFileAppender appender = new RollingFileAppender()
{
    Name = "DynamicAppender",
    LoggingLevel = "ALL",
    FilePath = "logs/dynamic.log",
    AppendToFile = true,
    RollingStyle = "Date",
    DatePattern = "yyyyMMdd",
    Layout = new Log4NetLayout
    {
        Type = "log4net.Layout.PatternLayout",
        ConversionPattern = pattern
    }
};

config.Appenders.Add(appender);
config.SaveConfigToFile("log4net.config");
XmlConfigurator.Configure(new System.IO.FileInfo("log4net.config"));

Getting the Generated XML Configuration

You can retrieve the XML configuration as a string without saving to a file:

Log4NetConfigHelper config = new Log4NetConfigHelper();
config.RootLevel = "ALL";
config.Appenders.Add(ConsoleAppender.GetDefault());

// Get appender names
List<string> appenderNames = config.Appenders.Select(a => a.Name).ToList();

// Get XML string
string xmlConfig = config.GetConfigXmlString(appenderNames);

Console.WriteLine(xmlConfig);

// Output:
// <log4net>
//   <root>
//     <level value="ALL" />
//     <appender-ref ref="ConsoleAppender" />
//   </root>
//   <appender name="ConsoleAppender" type="log4net.Appender.ColoredConsoleAppender">
//     ...
//   </appender>
// </log4net>

Common Pattern Layout Tokens

Use these tokens in your ConversionPattern:

• %date or %date{format} - Log timestamp (e.g., %date{yyyy-MM-dd HH:mm:ss})
• %thread - Thread ID
• %level or %-5level - Log level (padded to 5 characters)
• %logger - Logger name
• %message - Log message
• %exception - Exception information with stack trace
• %newline - Platform-specific line separator
• %username - Current Windows username
• %identity - Current thread identity
• %location - Full location (class.method:line)
• %class - Class name
• %method - Method name
• %file - Source file name
• %line - Line number
• %property{name} - Custom property value

Log Level Hierarchy

From least to most restrictive:

1. ALL - Logs everything
2. DEBUG - Detailed diagnostic information
3. INFO - Informational messages
4. WARN - Warning messages
5. ERROR - Error events
6. FATAL - Critical errors
7. OFF - Logging disabled

When you set a level, all levels above it are also logged. For example, setting INFO will log INFO, WARN, ERROR, and FATAL, but not DEBUG.

Best Practices

1. Always configure logging at application startup before any logging calls
2. Use meaningful appender names for easier debugging
3. Set appropriate root levels for production vs. development environments
4. Use date-based rolling for production to organize logs by day
5. Use size-based rolling for high-volume applications to prevent huge files
6. Include exception details using %exception in your pattern
7. Separate error logs for easier monitoring and alerting
8. Use JSON for log aggregation systems (ELK, Splunk, etc.)
9. Check generated XML by examining the saved log4net.config file
10. Test configuration in development before deploying to production

File Organization

Recommended folder structure:

YourApp/
├── bin/
│   └── log4net.config          (generated config file)
├── logs/
│   ├── application.log         (rolling text logs)
│   ├── application.20241201.log
│   ├── application.20241202.log
│   ├── errors.log              (error-only logs)
│   ├── application.json        (JSON logs)
│   └── application.20241201.json
└── Program.cs

Common Patterns

Development Configuration

config.RootLevel = "DEBUG";
config.Appenders.Add(ConsoleAppender.GetDefault());
// Shows all debug info in console

Production Configuration

config.RootLevel = "INFO";
// Rolling file for general logs
// Separate file for errors
// JSON for log aggregation

Testing Configuration

config.RootLevel = "WARN";
// Only warnings and errors during tests

Troubleshooting

Logs not appearing:

• Verify XmlConfigurator.Configure() is called before logging
• Check that generated log4net.config file exists
• Verify root level allows your log level
• Ensure output directory exists for file appenders

JSON appender not working:

• Install log4net.Ext.Json NuGet package
• Verify Members list is populated
• Check file path has .json extension

Configuration errors:

• Examine generated log4net.config XML for syntax errors
• Validate pattern syntax in ConversionPattern
• Ensure all required properties are set on appenders

Related Resources

• log4net Documentation
• log4net Pattern Layout
• log4net.Ext.Json