Control.ToString() should call Debugger.NotifyOfCrossThreadDependency()

Control.ToString() here calls Dispatcher.Invoke synchronously:
https://github.com/dotnet/wpf/blob/3cae6e13e3f4ba33a4e823e6dc345a3ac27deb92/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/Control.cs#L500-L502

When an instance of Control or a derived type is evaluated in the debugger from a background thread this results in a hang since other threads are suspended so the call to Dispatcher never returns.

Consider calling Debugger.NotifyOfCrossThreadDependency: https://referencesource.microsoft.com/#mscorlib/system/diagnostics/debugger.cs,564f13aa1fd18c60

Or even better, think of a simpler ToString() implementation that avoids calling Dispatcher in the first place. I'd even prefer just returning the type name when called from a background thread.

Derived types have the freedom to override ToString() anyway, providing more meaningful information in a safe way. This just covers the default case where derived types should just get a safe default behavior.