implemented SerilogLogger,

added to App Startup

Common/Common.csproj

@@ -8,6 +8,9 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="7.0.0" />
+    <PackageReference Include="Serilog" Version="2.12.0" />
+    <PackageReference Include="Serilog.Sinks.Debug" Version="2.0.0" />
+    <PackageReference Include="Serilog.Sinks.File" Version="5.0.0" />
   </ItemGroup>
 
 </Project>

Common/Logging/ILogger.cs

@@ -10,7 +10,7 @@ public interface ILogger
     /// <summary>
     /// Event that is thrown whenever a new log entry was entered with any Log method.
     /// </summary>
-    event EventHandler<NewLogEntryEventArgs> NewLogEntry;
+    event EventHandler<NewLogEntryEventArgs>? NewLogEntry;
 
     /// <summary>
     /// Initialize the Logger once before using it. 

Common/Logging/LogLevel.cs

@@ -2,13 +2,14 @@
 
 /// <summary>
 /// Level of a log entry.
+/// Listed from lowest priority to highest priority.
 /// </summary>
 public enum LogLevel
 { 
     Undefined = 0,
-    Error = 1,
+    Trace = 1,
-    Warn = 2,
+    Debug = 2,
     Info = 3,
-    Debug = 4,
+    Warn = 4,
-    Trace = 5
+    Error = 5
 }

Common/Logging/SerilogLogger.cs

@@ -0,0 +1,168 @@
+using Common.Logging;
+using Serilog;
+using Serilog.Core;
+using Serilog.Events;
+
+namespace Common.Logger;
+
+/// <summary>
+/// Implements a Logger that uses the Serilog package to create log entries and distributes them into different sinks.
+/// Implemented Sinks: File (rolling file), Debug (<see cref="System.Diagnostics.Debug"/>).
+/// </summary>
+public class SerilogLogger : Logging.ILogger
+{
+    private readonly LoggingLevelSwitch loggingLevelSwitch;
+    public event EventHandler<NewLogEntryEventArgs>? NewLogEntry;
+
+    /// <summary>
+    /// Constructor of a Logger that uses the Serilog package to create log entries and distributes them into different sinks.
+    /// </summary>
+    /// <param name="logFilePath">
+    /// path where the logfile shall be created. 
+    /// rolling file is created with daily interval. date is automatically added to file name.
+    /// Example: "C:/log/log-.txt"
+    /// </param>
+    /// <param name="logToDebug">
+    /// if true the log entries are written to <see cref="System.Diagnostics.Debug"/>. 
+    /// Minimum level is ignored for this log entries, therefore every log entry will be logged.
+    /// </param>
+    public SerilogLogger(string logFilePath, bool logToDebug)
+    {
+        // create logging level switch and initialized with lowest level
+        this.loggingLevelSwitch = new LoggingLevelSwitch() { MinimumLevel = Serilog.Events.LogEventLevel.Verbose };
+
+        // create logger instance
+        if (logToDebug)
+        {
+            Log.Logger = new LoggerConfiguration()
+                .WriteTo.Debug()
+                .WriteTo.File(logFilePath, 
+                    rollingInterval: RollingInterval.Day, 
+                    levelSwitch: loggingLevelSwitch,
+                    outputTemplate: "{Message:lj}")   // outputTemplate = plain message, formatting is done inside log entry
+                .CreateLogger();
+        }
+        else
+        {
+            Log.Logger = new LoggerConfiguration()
+                .WriteTo.File(logFilePath, 
+                    rollingInterval: RollingInterval.Day, 
+                    levelSwitch: loggingLevelSwitch,
+                    outputTemplate: "{Message:lj}")   // outputTemplate = plain message, formatting is done inside log entry
+                .CreateLogger();
+        }
+    }
+
+    public void Initialize()
+    {
+        this.Initialize(LogLevel.Trace);
+    }
+
+    public void Initialize(LogLevel minimumLogLevel)
+    {
+        this.SetMinimumLogLevel(minimumLogLevel);
+        // Nothing else to do for this logger
+    }
+
+    public void SetMinimumLogLevel(LogLevel newMinimumLogLevel)
+    {
+        this.loggingLevelSwitch.MinimumLevel = this.ConvertGenericToSerilogLogLevel(newMinimumLogLevel);
+    }
+
+    private LogEventLevel ConvertGenericToSerilogLogLevel(LogLevel newMinimumLogLevel) => newMinimumLogLevel switch
+    {
+        LogLevel.Undefined => LogEventLevel.Verbose,
+        LogLevel.Trace => LogEventLevel.Verbose,
+        LogLevel.Debug => LogEventLevel.Debug,
+        LogLevel.Info => LogEventLevel.Information,
+        LogLevel.Warn => LogEventLevel.Warning,
+        LogLevel.Error => LogEventLevel.Error,
+        _ => throw new NotImplementedException($"'{nameof(ConvertGenericToSerilogLogLevel)}()' does not contain an entry for {nameof(LogLevel)} {newMinimumLogLevel}"),
+    };
+
+    public void StopLogging()
+    {
+        Log.CloseAndFlush();
+    }
+
+    private void CreateLogEntry(LogEntry logEntry)
+    {
+        var serilogEventLevel = this.ConvertGenericToSerilogLogLevel(logEntry.LogLevel);
+        // formatting is done inside logEntry.ToString() method => therefore log plain message text with right category
+        switch (serilogEventLevel)
+        {
+            case LogEventLevel.Verbose:
+                Log.Verbose(logEntry.ToString());
+                break;
+
+            case LogEventLevel.Debug:
+                Log.Debug(logEntry.ToString());
+                break;
+
+            case LogEventLevel.Information:
+                Log.Information(logEntry.ToString());
+                break;
+
+            case LogEventLevel.Warning:
+                Log.Warning(logEntry.ToString());
+                break;
+
+            case LogEventLevel.Error:
+                Log.Error(logEntry.ToString());
+                break;
+
+            case LogEventLevel.Fatal:
+                Log.Error(logEntry.ToString());
+                break;
+
+            default:
+                throw new NotImplementedException($"'{nameof(CreateLogEntry)}()' does not contain an implementation for {nameof(LogEventLevel)} {serilogEventLevel}.");
+        }
+    }
+
+
+    #region Logging methods
+    public void LogTrace(string message, string category = "")
+    {
+        this.CreateLogEntry(new LogEntry { Category = category, LogLevel = LogLevel.Trace, Message = message });
+    }
+
+    public void LogDebug(string message, string category = "")
+    {
+        this.CreateLogEntry(new LogEntry { Category = category, LogLevel = LogLevel.Debug, Message = message });
+    }
+
+    public void LogInfo(string message, string category = "")
+    {
+        this.CreateLogEntry(new LogEntry { Category = category, LogLevel = LogLevel.Info, Message = message });
+    }
+
+    public void LogWarn(string message, string category = "")
+    {
+        this.CreateLogEntry(new LogEntry { Category = category, LogLevel = LogLevel.Warn, Message = message });
+    }
+
+    public void LogError(string message, string category = "")
+    {
+        this.CreateLogEntry(new LogEntry { Category = category, LogLevel = LogLevel.Error, Message = message });
+    }
+
+    public void LogException(Exception exception, string category = "")
+    {
+        this.CreateLogEntry(new LogEntry { Category = category, LogLevel = LogLevel.Error, Exception = exception });
+    }
+
+    public void LogException(Exception exception, string message, string category = "")
+    {
+        this.CreateLogEntry(
+            new LogEntry
+            {
+                Category = category,
+                LogLevel = LogLevel.Error,
+                Message = message,
+                Exception = exception
+            });
+    }
+    #endregion
+
+}

MultiTerm.Wpf/App.xaml.cs

@@ -1,10 +1,10 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
 using MultiTerm.Core.ViewModel;
-using Common.StartupHelpers;
 using System.Windows;
-using MultiTerm.Core.Common;
 using MultiTerm.Core.Helpers;
+using Common.Logging;
+using Common.Logger;
 
 namespace MultiTerm.Wpf;
 
@@ -19,6 +19,7 @@ public partial class App : Application
             .ConfigureServices((hostContext, services) =>
             {
                 services.AddSingleton<MainWindow>();
+                services.AddSingleton<ILogger>(new SerilogLogger("C:/log/multiterm-log-.txt", true));
 
                 // viewmodels
                 services.AddSingleton<ShellViewModel>();
@@ -33,6 +34,11 @@ public partial class App : Application
     {
         await AppHost!.StartAsync();
 
+        // create logger and initialize
+        var logger = AppHost.Services.GetRequiredService<ILogger>();
+        logger.Initialize(LogLevel.Trace);
+        logger.LogInfo("Application started.", nameof(App));
+
         // instanciate startup form and show
         var startupForm = AppHost.Services.GetRequiredService<MainWindow>();
         startupForm.Show();
@@ -42,6 +48,11 @@ public partial class App : Application
 
     protected override async void OnExit(ExitEventArgs e)
     {
+        // log application exit and stop logger (if still available)
+        var logger = AppHost!.Services.GetRequiredService<ILogger>();
+        logger?.LogInfo("Application exited.", nameof(App));
+        logger?.StopLogging();
+
         await AppHost!.StopAsync();
         base.OnExit(e);
     }