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

- [ ] Quirked
- [ ] Build-time break

### Recommended Action
Upgrade to .Net 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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