Bring back C# sample logging!

samples/CSharpAvalonia/MainWindow.axaml.cs

@@ -4,6 +4,7 @@ using Avalonia.Controls;
 using Avalonia.Interactivity;
 using Avalonia.Threading;
 using Velopack;
+using Velopack.Logging;
 
 namespace CSharpAvalonia;
 
@@ -19,6 +20,8 @@ public partial class MainWindow : Window
         var updateUrl = SampleHelper.GetReleasesDir(); // replace with your update path/url
         _um = new UpdateManager(updateUrl);
 
+        TextLog.Text = Program.Log.ToString();
+        Program.Log.LogUpdated += LogUpdated;
         UpdateStatus();
     }
 
@@ -29,7 +32,7 @@ public partial class MainWindow : Window
             // ConfigureAwait(true) so that UpdateStatus() is called on the UI thread
             _update = await _um.CheckForUpdatesAsync().ConfigureAwait(true);
         } catch (Exception ex) {
-            LogMessage("Error checking for updates", ex);
+            Program.Log.LogError(ex, "Error checking for updates");
         }
 
         UpdateStatus();
@@ -42,7 +45,7 @@ public partial class MainWindow : Window
             // ConfigureAwait(true) so that UpdateStatus() is called on the UI thread
             await _um.DownloadUpdatesAsync(_update, Progress).ConfigureAwait(true);
         } catch (Exception ex) {
-            LogMessage("Error downloading updates", ex);
+            Program.Log.LogError(ex, "Error downloading updates");
         }
 
         UpdateStatus();
@@ -53,16 +56,12 @@ public partial class MainWindow : Window
         _um.ApplyUpdatesAndRestart(_update);
     }
 
-    private void LogMessage(string text, Exception e = null)
+    private void LogUpdated(object sender, LogUpdatedEventArgs e)
     {
         // logs can be sent from other threads
         Dispatcher.UIThread.InvokeAsync(
             () => {
-                TextLog.Text += text + Environment.NewLine;
+                TextLog.Text = e.Text;
-                if (e != null) {
-                    TextLog.Text += e.ToString() + Environment.NewLine;
-                }
-
                 ScrollLog.ScrollToEnd();
             });
     }
@@ -78,7 +77,7 @@ public partial class MainWindow : Window
 
     private void Working()
     {
-        LogMessage("");
+        Program.Log.LogInformation("");
         BtnCheckUpdate.IsEnabled = false;
         BtnDownloadUpdate.IsEnabled = false;
         BtnRestartApply.IsEnabled = false;

samples/CSharpAvalonia/MemoryLogger.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Text;
+using Velopack.Logging;
+
+namespace CSharpAvalonia;
+
+public class LogUpdatedEventArgs : EventArgs
+{
+    public string Text { get; set; }
+}
+
+public class MemoryLogger : IVelopackLogger
+{
+    public event EventHandler<LogUpdatedEventArgs> LogUpdated;
+    private readonly StringBuilder _sb = new StringBuilder();
+
+    public IDisposable BeginScope<TState>(TState state)
+    {
+        return null;
+    }
+
+    public override string ToString()
+    {
+        lock (_sb) {
+            return _sb.ToString();
+        }
+    }
+
+    public void Log(VelopackLogLevel logLevel, string message, Exception exception)
+    {
+        lock (_sb) {
+            message = $"{logLevel}: {message}";
+            if (exception != null) message += "\n" + exception.ToString();
+            Console.WriteLine("log: " + message);
+            _sb.AppendLine(message);
+            LogUpdated?.Invoke(this, new LogUpdatedEventArgs { Text = _sb.ToString() });
+        }
+    }
+}

samples/CSharpAvalonia/Program.cs

@@ -6,6 +6,8 @@ namespace CSharpAvalonia;
 
 class Program
 {
+    public static MemoryLogger Log { get; private set; } = new();
+
     // Initialization code. Don't use any Avalonia, third-party APIs or any
     // SynchronizationContext-reliant code before AppMain is called: things aren't initialized
     // yet and stuff might break.
@@ -16,6 +18,7 @@ class Program
             // It's important to Run() the VelopackApp as early as possible in app startup.
             VelopackApp.Build()
                 .OnFirstRun((v) => { /* Your first run code here */ })
+                .SetLogger(Log)
                 .Run();
 
             // Now it's time to run Avalonia

samples/CSharpWpf/App.xaml.cs

@@ -5,6 +5,8 @@ namespace CSharpWpf
 {
     public partial class App : Application
     {
+        public static MemoryLogger Log { get; private set; } = new();
+
         // Since WPF has an "automatic" Program.Main, we need to create our own.
         // In order for this to work, you must also add the following to your .csproj:
         // <StartupObject>CSharpWpf.App</StartupObject>
@@ -15,6 +17,7 @@ namespace CSharpWpf
                 // It's important to Run() the VelopackApp as early as possible in app startup.
                 VelopackApp.Build()
                     .OnFirstRun((v) => { /* Your first run code here */ })
+                    .SetLogger(Log)
                     .Run();
 
                 // We can now launch the WPF application as normal.

samples/CSharpWpf/MainWindow.xaml.cs

@@ -1,6 +1,7 @@
 using System.Text;
 using System.Windows;
 using Velopack;
+using Velopack.Logging;
 
 namespace CSharpWpf
 {
@@ -16,6 +17,8 @@ namespace CSharpWpf
             string updateUrl = SampleHelper.GetReleasesDir(); // replace with your update url
             _um = new UpdateManager(updateUrl);
 
+            TextLog.Text = App.Log.ToString();
+            App.Log.LogUpdated += LogUpdated;
             UpdateStatus();
         }
 
@@ -26,7 +29,7 @@ namespace CSharpWpf
                 // ConfigureAwait(true) so that UpdateStatus() is called on the UI thread
                 _update = await _um.CheckForUpdatesAsync().ConfigureAwait(true);
             } catch (Exception ex) {
-                LogMessage("Error checking for updates", ex);
+                App.Log.LogError(ex, "Error checking for updates");
             }
             UpdateStatus();
         }
@@ -38,7 +41,7 @@ namespace CSharpWpf
                 // ConfigureAwait(true) so that UpdateStatus() is called on the UI thread
                 await _um.DownloadUpdatesAsync(_update, Progress).ConfigureAwait(true);
             } catch (Exception ex) {
-                LogMessage("Error downloading updates", ex);
+                App.Log.LogError(ex, "Error downloading updates");
             }
             UpdateStatus();
         }
@@ -48,14 +51,11 @@ namespace CSharpWpf
             _um.ApplyUpdatesAndRestart(_update);
         }
 
-        private void LogMessage(string text, Exception e = null)
+        private void LogUpdated(object sender, LogUpdatedEventArgs e)
         {
             // logs can be sent from other threads
             this.Dispatcher.InvokeAsync(() => {
-                TextLog.Text += text + Environment.NewLine;
+                TextLog.Text = e.Text;
-                if (e != null) {
-                    TextLog.Text += e.ToString() + Environment.NewLine;
-                }
                 ScrollLog.ScrollToEnd();
             });
         }
@@ -70,7 +70,7 @@ namespace CSharpWpf
 
         private void Working()
         {
-            LogMessage("");
+            App.Log.LogInformation("");
             BtnCheckUpdate.IsEnabled = false;
             BtnDownloadUpdate.IsEnabled = false;
             BtnRestartApply.IsEnabled = false;

samples/CSharpWpf/MemoryLogger.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Text;
+using Velopack.Logging;
+
+namespace CSharpWpf;
+
+public class LogUpdatedEventArgs : EventArgs
+{
+    public string Text { get; set; }
+}
+
+public class MemoryLogger : IVelopackLogger
+{
+    public event EventHandler<LogUpdatedEventArgs> LogUpdated;
+    private readonly StringBuilder _sb = new StringBuilder();
+
+    public IDisposable BeginScope<TState>(TState state)
+    {
+        return null;
+    }
+
+    public override string ToString()
+    {
+        lock (_sb) {
+            return _sb.ToString();
+        }
+    }
+
+    public void Log(VelopackLogLevel logLevel, string message, Exception exception)
+    {
+        lock (_sb) {
+            message = $"{logLevel}: {message}";
+            if (exception != null) message += "\n" + exception.ToString();
+            Console.WriteLine("log: " + message);
+            _sb.AppendLine(message);
+            LogUpdated?.Invoke(this, new LogUpdatedEventArgs { Text = _sb.ToString() });
+        }
+    }
+}

src/lib-csharp/VelopackApp.cs

@@ -35,6 +35,7 @@ namespace Velopack
         private string[]? _args;
         private bool _autoApply = true;
         private IVelopackLocator? _customLocator;
+        private IVelopackLogger? _customLogger;
 
         private VelopackApp()
         {
@@ -74,6 +75,17 @@ namespace Velopack
             return this;
         }
 
+        /// <summary>
+        /// Adds a custom logger to the Velopack application. This will be used for all Velopack diagnostic
+        /// messages in addition to the default log file location. This will be cached and re-used throughout
+        /// the lifetime of the application. If you have also provided a custom locator, this logger will be ignored.
+        /// </summary>
+        public VelopackApp SetLogger(IVelopackLogger logger)
+        {
+            _customLogger = logger;
+            return this;
+        }
+
         /// <summary>
         /// This hook is triggered when the application is started for the first time after installation.
         /// </summary>
@@ -151,13 +163,6 @@ namespace Velopack
         {
             var args = _args ?? Environment.GetCommandLineArgs().Skip(1).ToArray();
 
-            // internal hook run by the Velopack tooling to check everything is working
-            if (args.Length >= 1 && args[0].Equals("--veloapp-version", StringComparison.OrdinalIgnoreCase)) {
-                Console.WriteLine(VelopackRuntimeInfo.VelopackNugetVersion);
-                Exit(0);
-                return;
-            }
-
             if (VelopackLocator.IsCurrentSet) {
                 VelopackLocator.Current.Log.Error(
                     "VelopackApp.Build().Run() was called more than once. This is not allowed and can lead to unexpected behaviour.");
@@ -167,7 +172,7 @@ namespace Velopack
                 VelopackLocator.SetCurrentLocator(_customLocator);
             }
 
-            var locator = VelopackLocator.GetCurrentOrCreateDefault();
+            var locator = VelopackLocator.GetCurrentOrCreateDefault(_customLogger);
             var log = locator.Log;
 
             log.Info($"Starting VelopackApp.Run (library version {VelopackRuntimeInfo.VelopackNugetVersion}).");