this.Log()

0HowAwesomeIsThis.cs

public class SomeClass {

  public void SomeMethod() {
    this.Log().Info(() => "Here is a log message with params which can be in Razor Views as well: '{0}'".FormatWith(typeof(SomeClass).Name));
  }

}

1TheBootStrapRegistration.cs

 Log.InitializeWith<Log4NetLog>();

2RootNamespaceLogExtensions.cs

/// <summary>
/// Extensions to help make logging awesome
/// </summary>
public static class LogExtensions
{
    /// <summary>
    /// Concurrent dictionary that ensures only one instance of a logger for a type.
    /// </summary>
    private static readonly Lazy<ConcurrentDictionary<string,ILog>> _dictionary = new Lazy<ConcurrentDictionary<string, ILog>>(()=>new ConcurrentDictionary<string, ILog>());

    /// <summary>
    /// Gets the logger for <see cref="T"/>.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="type">The type to get the logger for.</param>
    /// <returns>Instance of a logger for the object.</returns>
    public static ILog Log<T>(this T type)
    {
        string objectName = typeof(T).FullName;
        return Log(objectName);
   }

    /// <summary>
    /// Gets the logger for the specified object name.
    /// </summary>
    /// <param name="objectName">Either use the fully qualified object name or the short. If used with Log&lt;T&gt;() you must use the fully qualified object name"/></param>
    /// <returns>Instance of a logger for the object.</returns>
    public static ILog Log(this string objectName)
    {
        return _dictionary.Value.GetOrAdd(objectName, Infrastructure.Logging.Log.GetLoggerFor);
    }
}

3StaticLogGateway.cs

/// <summary>
/// Logger type initialization
/// </summary>
public static class Log
{
    private static Type _logType = typeof(NullLog);
    private static ILog _logger;

    /// <summary>
    /// Sets up logging to be with a certain type
    /// </summary>
    /// <typeparam name="T">The type of ILog for the application to use</typeparam>
    public static void InitializeWith<T>() where T : ILog, new()
    {
        _logType = typeof(T);
    }

    /// <summary>
    /// Sets up logging to be with a certain instance. The other method is preferred.
    /// </summary>
    /// <param name="loggerType">Type of the logger.</param>
    /// <remarks>This is mostly geared towards testing</remarks>
    public static void InitializeWith(ILog loggerType)
    {
        _logType = loggerType.GetType();
        _logger = loggerType;
    }

    /// <summary>
    /// Initializes a new instance of a logger for an object.
    /// This should be done only once per object name.
    /// </summary>
    /// <param name="objectName">Name of the object.</param>
    /// <returns>ILog instance for an object if log type has been intialized; otherwise null</returns>
    public static ILog GetLoggerFor(string objectName)
    {
        var logger = _logger;

        if (_logger == null)
        {
            logger = Activator.CreateInstance(_logType) as ILog;
            if (logger != null)
            {
                logger.InitializeFor(objectName);
            }
        }

        return logger;
    }
}

4ILogInterfaces.cs

/// <summary>
/// Custom interface for logging messages
/// </summary>
public interface ILog
{
    /// <summary>
    /// Initializes the instance for the logger name
    /// </summary>
    /// <param name="loggerName">Name of the logger</param>
    void InitializeFor(string loggerName);
    
    /// <summary>
    /// Debug level of the specified message. The other method is preferred since the execution is deferred.
    /// </summary>
    /// <param name="message">The message.</param>
    /// <param name="formatting">The formatting.</param>
    void Debug(string message, params object[] formatting);
    /// <summary>
    /// Debug level of the specified message.
    /// </summary>
    /// <param name="message">The message.</param>
    void Debug(Func<string> message);
    /// <summary>
    /// Info level of the specified message. The other method is preferred since the execution is deferred.
    /// </summary>
    /// <param name="message">The message.</param>
    /// <param name="formatting">The formatting.</param>
    void Info(string message, params object[] formatting);
    /// <summary>
    /// Info level of the specified message.
    /// </summary>
    /// <param name="message">The message.</param>
    void Info(Func<string> message);
    /// <summary>
    /// Warn level of the specified message. The other method is preferred since the execution is deferred.
    /// </summary>
    /// <param name="message">The message.</param>
    /// <param name="formatting">The formatting.</param>
    void Warn(string message, params object[] formatting);
    /// <summary>
    /// Warn level of the specified message.
    /// </summary>
    /// <param name="message">The message.</param>
    void Warn(Func<string> message);
    /// <summary>
    /// Error level of the specified message. The other method is preferred since the execution is deferred.
    /// </summary>
    /// <param name="message">The message.</param>
    /// <param name="formatting">The formatting.</param>
    void Error(string message, params object[] formatting);
    /// <summary>
    /// Error level of the specified message.
    /// </summary>
    /// <param name="message">The message.</param>
    void Error(Func<string> message);
    /// <summary>
    /// Fatal level of the specified message. The other method is preferred since the execution is deferred.
    /// </summary>
    /// <param name="message">The message.</param>
    /// <param name="formatting">The formatting.</param>
    void Fatal(string message, params object[] formatting);
    /// <summary>
    /// Fatal level of the specified message.
    /// </summary>
    /// <param name="message">The message.</param>
    void Fatal(Func<string> message);
}

/// <summary>
/// Ensures a default constructor for the logger type
/// </summary>
/// <typeparam name="T"></typeparam>
public interface ILog<T> where T : new()
{
}
}

5DefaultNullLogger.cs

/// <summary>
/// The default logger until one is set.
/// </summary>
public class NullLog : ILog, ILog<NullLog>
{
    public void InitializeFor(string loggerName)
    {
    }

    public void Debug(string message, params object[] formatting)
    {
    }

    public void Debug(Func<string> message)
    {
    }

    public void Info(string message, params object[] formatting)
    {
    }

    public void Info(Func<string> message)
    {
    }

    public void Warn(string message, params object[] formatting)
    {
    }

    public void Warn(Func<string> message)
    {
    }

    public void Error(string message, params object[] formatting)
    {
    }

    public void Error(Func<string> message)
    {
    }

    public void Fatal(string message, params object[] formatting)
    {
    }

    public void Fatal(Func<string> message)
    {
    }
}

6Log4NetLogger.cs

using System;
using log4net;
using log4net.Config;

[assembly: XmlConfigurator(Watch = true)]
namespace Some.Namespace {

/// <summary>
/// Log4net logger implementing special ILog class
/// </summary>
public class Log4NetLog : ILog, ILog<Log4NetLog>
{
    private global::log4net.ILog _logger;
    
    public void InitializeFor(string loggerName)
    {
        _logger = LogManager.GetLogger(loggerName);
    }

    public void Debug(string message, params object[] formatting)
    {
        if (_logger.IsDebugEnabled) _logger.DebugFormat(DecorateMessageWithAuditInformation(message), formatting);
    }

    public void Debug(Func<string> message)
    {
        if (_logger.IsDebugEnabled) _logger.Debug(DecorateMessageWithAuditInformation(message.Invoke()));
    }

    public void Info(string message, params object[] formatting)
    {
       if (_logger.IsInfoEnabled) _logger.InfoFormat(DecorateMessageWithAuditInformation(message), formatting);
    }

    public void Info(Func<string> message)
    {
        if (_logger.IsInfoEnabled) _logger.Info(DecorateMessageWithAuditInformation(message.Invoke()));
    }

    public void Warn(string message, params object[] formatting)
    {
       if (_logger.IsWarnEnabled) _logger.WarnFormat(DecorateMessageWithAuditInformation(message), formatting);
    }

    public void Warn(Func<string> message)
    {
        if (_logger.IsWarnEnabled) _logger.Warn(DecorateMessageWithAuditInformation(message.Invoke()));
    }

    public void Error(string message, params object[] formatting)
    {
        // don't need to check for enabled at this level
        _logger.ErrorFormat(DecorateMessageWithAuditInformation(message), formatting);
    }

    public void Error(Func<string> message)
    {
        // don't need to check for enabled at this level
         _logger.Error(DecorateMessageWithAuditInformation(message.Invoke()));
    }

    public void Fatal(string message, params object[] formatting)
    {
        // don't need to check for enabled at this level
        _logger.FatalFormat(DecorateMessageWithAuditInformation(message), formatting);
    }

    public void Fatal(Func<string> message)
    {
        // don't need to check for enabled at this level
        _logger.Fatal(DecorateMessageWithAuditInformation(message.Invoke()));
    }

    public string DecorateMessageWithAuditInformation(string message)
    {
        string currentUserName = ApplicationParameters.GetCurrentUserName();
        if (!string.IsNullOrWhiteSpace(currentUserName))
        {
            return "{0} - {1}".FormatWith(message, currentUserName);
        }

        return message;
    }

}
}

7FormatWithExtension.cs

public static class StringExtensions
{
    /// <summary>
    /// Formats string with the formatting passed in. This is a shortcut to string.Format().
    /// </summary>
    /// <param name="input">The input.</param>
    /// <param name="formatting">The formatting.</param>
    /// <returns>A formatted string.</returns>
    public static string FormatWith(this string input, params object[] formatting)
    {
        return string.Format(input, formatting);
    }

}

Look at the following gits https://gist.github.com/4299744 and tell me what you think.