DecoratorLogger_2

 public interface ILogger
    {
        void Exception(string message, Exception ex);
        void Info(string message);
        void Warning(string message);
        void Progress(ProgressDataEventArgs progressData); //new method required for logging progress
    }

    public class MemoryLogger : ILogger
    {
        public List<LogLine> Log { get; }
        private readonly ILogger _internalLogger; //internal logger that this logger will decorate

        public MemoryLogger(ILogger internalLogger)
        {
            Log = new List<LogLine>();
            _internalLogger = internalLogger;
        }
        public void Exception(string message, Exception ex)
        {
            Log.Add(new LogLine(LogLine.SeverityLevels.Error, message, ex));
            _internalLogger.Exception(message, ex); //each public method does its job and calls internal logger method (which may do the same).
        }

        public void Info(string message)
        {
            Log.Add(new LogLine(LogLine.SeverityLevels.Info, message));
            _internalLogger.Info(message);
        }

        public void Warning(string message)
        {
            Log.Add(new LogLine(LogLine.SeverityLevels.Warn, message));
            _internalLogger.Warning(message);
        }

        public void Progress(ProgressDataEventArgs progressData)
        {
            _internalLogger.Progress(progressData);
        }

        public override string ToString()
        {
            var sb = new StringBuilder();
            foreach (var logLine in Log)
                sb.AppendLine(logLine.ToString());
            return sb.ToString();
        }
    }

    public class CmdletLogger : ILogger
    {
        private readonly Cmdlet _cmdlet;

        public CmdletLogger(Cmdlet cmdlet)
        {
            _cmdlet = cmdlet;
        }

        public void Exception(string message, Exception ex)
        {
            _cmdlet.WriteError(new ErrorRecord(ex, Guid.NewGuid().ToString(), ErrorCategory.NotSpecified, message));
        }

        public void Info(string message)
        {
            _cmdlet.WriteInformation(message, new string[] { });
        }

        public void Warning(string message)
        {
            _cmdlet.WriteWarning(message);
        }

        public void Progress(ProgressDataEventArgs progressData)
        {
            var progressRecord = new ProgressRecord(progressData.ActivityId, progressData.Activity, progressData.StatusDescription)
            {
                PercentComplete = progressData.AllStepsCount == 0 ? 100 : (progressData.CurrentStepNo * 100 / progressData.AllStepsCount),
                RecordType = ProgressRecordType.Processing
            };
            _cmdlet.WriteProgress(progressRecord);
        }
    }

 public class ProgressDataEventArgs : EventArgs
    {
        public int ActivityId { get; }
        public string Activity { get; }
        public string StatusDescription { get; }
        public int CurrentStepNo { get; }
        public int AllStepsCount { get; }

        public ProgressDataEventArgs(int activityId, string activity, string statusDescription, int currentStepNo, int allStepsCount)
        {
            ActivityId = activityId;
            Activity = activity;
            StatusDescription = statusDescription;
            CurrentStepNo = currentStepNo;
            AllStepsCount = allStepsCount;
        }
    }