Sometimes PreviousContainer got missing for LayoutAnchorable after float window is closed.

[yyjdelete]

1. Run TestApp from this repo(a54b7d5);
2. Drag and drop the right tabs(Tool Window 1+2) to the same float window;
3. Right click and hide Tool Window 1;
4. Drag and drop Tool Window 2 to the top of the MainWindow;
5. Click Tools/Tool Window 1

Expected:

It should still possbile to show Tool Window 1, either in an new float window or the same position as Tool Window 2;

Actual:

Tool Window 1 can not be shown, and see PreviousContainerId is missing from the output Layout.config;

[LyonJack]

There is an error on my codes,I will resolve it today

[Dirkster99]

I am not sure about this fix - I am getting an exception after (Step 4) dropping Tool Window 2 back into the DocumentPane and (step 5) trying to show Tool Window 1

This is the exception that I see after step 5 in the above workflow:

System.NullReferenceException
  HResult=0x80004003
  Message=Object reference not set to an instance of an object.
  Source=AvalonDock
  StackTrace:
   at AvalonDock.Layout.LayoutContent.set_IsActive(Boolean value) in ...\AvalonDock-master\source\Components\AvalonDock\Layout\LayoutContent.cs:line 182

[LyonJack]

There is an error on my codes,I will resolve it today

[Dirkster99]

I tried a similar fix myself yesterday but failed with the same result its failing now 😞

• When you follow the above workflow, Tool Window 1 does not re-appear in Step 5 (which is the objective of this issue).
• When I repeat step 5 twice as the last step of the workflow I get a different exception in the client code:

System.InvalidOperationException
  HResult=0x80131509
  Message=Sequence contains no matching element
  Source=System.Linq
  StackTrace:
   at System.Linq.ThrowHelper.ThrowNoMatchException()
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source, Func`2 predicate)
   at TestApp.MainWindow.OnShowToolWindow1(Object sender, RoutedEventArgs e) in ...AvalonDock-master\source\TestApp\MainWindow.xaml.cs:line 199
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.Controls.MenuItem.InvokeClickAfterRender(Object arg)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
   at System.Windows.Threading.DispatcherOperation.InvokeImpl()
   at MS.Internal.CulturePreservingExecutionContext.CallbackWrapper(Object obj)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)

[Dirkster99]

Closed the issue by accident - reopen since the issue is not fixed