Log4NetListener

using log4net;
using log4net.Appender;
using log4net.Config;
using log4net.Layout;
using log4net.Repository.Hierarchy;
using System;
using System.IO;
using System.Linq;

namespace EZX.Tools.TestTools
{
    public class Log4NetListener : IDisposable
    {

        #region Static Properties and Fields
        private const string BaseAppenderName = "UnitTestAppender-";
        private static readonly string UniqueID = UniqueIDGenerator.GetNextID();
        private static int counter;

        public static string AppenderNamePrefix { get; private set; }

        private static Logger Root
        {
            get { return ((Hierarchy)LogManager.GetRepository()).Root; }
        }
        #endregion

        static Log4NetListener()
        {
            AppenderNamePrefix = BaseAppenderName + UniqueID;
        }

        private MemoryAppender memAppender;

        /// <summary>
        /// Attaches the listener so it would capture any log messages written.
        /// </summary>
        /// <param name="appenderName">Name of Appender which has a PatternLayout to use for writing test log messages</param>
        /// <exception cref="InvalidOperationException">if no Appender exists with specified name</exception>
        public void AttachLogListener(string appenderName)
        {
            var appender = LogManager.GetRepository().GetAppenders().Where(a => a.Name == appenderName).ToList();
            if (appender.Count == 0)
            {
                throw new InvalidOperationException(string.Format("Unable to find Appender named [{0}]! unable to setup Appender...", appenderName));
            }
            var patternLayout = ((PatternLayout)((AppenderSkeleton)(appender.First())).Layout);
            CreateAppender(patternLayout);

        }


        public void AttachLogListener()
        {
            CreateAppender(null);
        }

        private void CreateAppender(ILayout patternLayout)
        {
            memAppender = new MemoryAppender { Layout = patternLayout, Name = GetNextAppenderName() };
            BasicConfigurator.Configure(memAppender);
        }

        private static string GetNextAppenderName()
        {
            return string.Concat(AppenderNamePrefix, ++counter);
        }

        /// <summary>
        /// Gets the message written to log. Use this method only after AttachLogListener() was called
        /// and a message was written to log4net afterwards.
        /// </summary>
        public string GetRenderedMessage()
        {
            if (memAppender == null)
            {
                throw new InvalidOperationException("The listener was not attached. Make sure you call AttachLogListener() before writing to log.");
            }
            var events = memAppender.GetEvents();
            string logMessage;
            using (var writer = new StringWriter())
            {
                foreach (var ev in events)
                {
                    memAppender.Layout.Format(writer, ev);
                }
                logMessage = writer.ToString();
            }
            return logMessage;
        }

        /// <summary>
        /// Gets all message logged by this appender.
        /// </summary>
        /// <returns></returns>
        public string GetMessages()
        {
            if (memAppender == null)
            {
                throw new InvalidOperationException("The listener was not attached. Make sure you call AttachLogListener() before writing to log.");
            }
            var events = memAppender.GetEvents();
            string logMessage;
            using (var writer = new StringWriter())
            {
                foreach (var ev in events)
                {
                    ev.WriteRenderedMessage(writer);
                }
                logMessage = writer.ToString();
            }
            return logMessage;
        }

        public static void RemoveAll()
        {
            var root = Root;

            var testAppenders = LogManager.GetRepository().GetAppenders()
                .Where(x => x.Name.StartsWith(AppenderNamePrefix));

            foreach (var testAppender in testAppenders)
            {
                root.RemoveAppender(testAppender);
            }


        }

        /// <inheritdoc />
        public void Dispose()
        {
            Root.RemoveAppender(memAppender);
        }


    }

}