## Crash in Selector when removing an item from a custom INCC collection

### Scope
Minor

### Version Introduced
4.7

### Version Reverted
4.7.1

### Source Analyzer Status
NotPlanned

### Change Description
An `T:System.InvalidOperationException` can occur in the following scenario:
  * The ItemsSource for a `T:System.Windows.Controls.Primitives.Selector` is a collection with a custom
	implementation of `T:System.Collections.Specialized.INotifyCollectionChanged`.
  * The selected item is removed from the collection.
  * The `T:System.Collections.Specialized.NotifyCollectionChangedEventArgs` has 
    `P:System.Collections.Specialized.NotifyCollectionChangedEventArgs.OldStartingIndex` = -1 
	(indicating an unknown position).

The exception's callstack begins
   at System.Windows.Threading.Dispatcher.VerifyAccess()
   at System.Windows.DependencyObject.GetValue(DependencyProperty dp)
   at System.Windows.Controls.Primitives.Selector.GetIsSelected(DependencyObject element)

This exception can occur in .NET Framework 4.5 if the application has more than one Dispatcher thread.
In .NET Framework 4.7 the exception can also occur in applications with a single Dispatcher thread.
The issue is fixed in .NET Framework 4.7.1.

- [ ] Quirked
- [ ] Build-time break

### Recommended Action
Upgrade to .NET Framework 4.7.1.

### Affected APIs
 * Not detectable via API analysis

### Category
Windows Presentation Foundation (WPF)

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    ### Original Bug
    424259
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