InvalidOperationException when KeyBindings change while a KeyBinding is being handled

[Fusion86]

AvaloniaUI throws an InvalidOperationException when currentHandler.KeyBindings changes while handling a KeyBinding in the same list. This can happen when you load a new view using a command, and this new view has a HotKey.

System.InvalidOperationException
  HResult=0x80131509
  Message=Collection was modified; enumeration operation may not execute.
  Source=System.Private.CoreLib
  StackTrace:
   at System.ThrowHelper.ThrowInvalidOperationException_InvalidOperation_EnumFailedVersion()
   at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
   at Avalonia.Input.KeyboardDevice.ProcessRawEvent(RawInputEventArgs e)
   at Avalonia.Input.InputManager.ProcessInput(RawInputEventArgs e)
   at Avalonia.Win32.WindowImpl.AppWndProc(IntPtr hWnd, UInt32 msg, IntPtr wParam, IntPtr lParam)
   at Avalonia.Win32.WindowImpl.WndProc(IntPtr hWnd, UInt32 msg, IntPtr wParam, IntPtr lParam)
   at Avalonia.Win32.Interop.UnmanagedMethods.DispatchMessage(MSG& lpmsg)
   at Avalonia.Win32.Win32Platform.RunLoop(CancellationToken cancellationToken)
   at Avalonia.Threading.Dispatcher.MainLoop(CancellationToken cancellationToken)
   at Avalonia.Controls.ApplicationLifetimes.ClassicDesktopStyleApplicationLifetime.Start(String[] args)
   at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime[T](T builder, String[] args, ShutdownMode shutdownMode)
   at BindingsInvalidOperationException.Program.Main(String[] args) in C:\Users\Wouter\source\repos\BindingsInvalidOperationException\Program.cs:line 11

I created a repo which can be used to reproduce this issue.

How to trigger the crash:

1. Run the BindingsInvalidOperationException project
2. Press CTRL+N
   2.1 This executes the AddTabCommand (see MainWindow.xaml -> Menu -> MenuItem -> HotKey)
   2.2 The AddTabCommand adds a new TabPageViewModel to the TabControl
   2.3 The TabControl loads a new TabPageView.xaml
   2.4 The TabPageView has two buttons with a HotKey
   2.5 I guess these new HotKeys are somehow added to the KeyBindings, which crashes the foreach loop.

An interesting fact is that it doesn't crash when you click the Add Tab MenuItem with your mouse. This is probably because the foreach loop is never executed in those cases.

Another funfact: if you click the Add Tab menu item once, so that it adds the HotKeys without crashing, you can then use CTRL+N to open more tabs and it doesn't crash. This is probably because it doesn't add the HotKeys because they already are inside the list.

I created this fix. It seems to work fine for my project, but I wouldn't know whether this is the best solution for the problem. I'll open a PR, but I'll also leave this issue open in case this solution is not acceptable.

This is all tested on 0.10.0-preview6.

[davidtimovski]

I'm experiencing this same issue on my project here. It works fine when the packages are version 0.10.0 but when I bump them up to 0.10.1 this problem occurs when using HotKeys (pressing Enter to save a new note).