System.NullReferenceException at Window.Close() from Opened or Activated handler

When calling Close() from inside an event handler for Opened or Activated, an uncaught System.NullReferenceException occurs in the Main() function of the program.

Expected behavior Window closes (and application terminates when using default shutdown mode).

Steps to reproduce Create an Avalonia Application and change the code in MainWindow.cs as follows:

  public class MainWindow : Window
  {
      public MainWindow()
      {
          Opened += OnOpened;
          // Uncomment the line above and comment the line above
          //Activated += OnActivated;
          InitializeComponent();
      }
  
      private void OnActivated(object? sender, EventArgs e)
      {
          Close(); // <= Causes an exception
      }
  
      private void OnOpened(object? sender, EventArgs e)
      {
          Close(); // <= Causes an exception
      }
  
      private void InitializeComponent()
      {
          AvaloniaXamlLoader.Load(this);
      }
  }

The exception occurs in Main():

  [STAThread]
  public static void Main(string[] args) => BuildAvaloniaApp()
           .StartWithClassicDesktopLifetime(args); // <= Uncaught System.NullReferenceException

Desktop

• OS: Windows 10
• Version 0.10.10 and 0.10.11

Additional context If you show a dialog window before calling Close(), the behavior is as expected:

  public class MainWindow : Window
  {
      public MainWindow()
      {
          Opened += OnOpened;
          InitializeComponent();
      }
  
      private async void OnOpened(object? sender, EventArgs e)
      {
          Window dialogWindow = new VersionUpgradeWindow();
          await dialogWindow.ShowDialog(this);
          Close(); // <== No exception, window and application closes
      }
  
      private void InitializeComponent()
      {
          AvaloniaXamlLoader.Load(this);
      }
  }

[Gillibald]

OnActivated and OnOpened should only be raised when the Window is initialized so this is a bug

[Maikelsoft]

Oh yeah…the stack trace 😃

   at Avalonia.Controls.ApplicationLifetimes.ClassicDesktopStyleApplicationLifetime.Start(String[] args) in /_/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 132
   at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime[T](T builder, String[] args, ShutdownMode shutdownMode) in /_/src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs:line 187
   at Maikelsoft.PhotoTool.AvaloniaUI.Program.Main(String[] args) in ************************\Program.cs:line 15

Exception source: Avalonia.Controls