[Enhancement] [vNext] Implement SelectorRegionAdapter

[DamianSuess]

Description

As a user, I'd like to use SelectorRegionAdapter with for Avalonia's namespace, Avalonia.Styling.

Context

This includes:

• SelectorRegionAdapter
• SelectorItemsSourceSyncBehavior
• SelectorRegionAdapterFixture

[dhhunter]

I am unfamiliar with SelectorRegionAdapterFixture, where would I find that in the Source? Shouldn't SelectorRegionAdapter be derived from RegionAdapterBase of SelectingItemsControl? I started working on that feature myself in an attempt to get TabControl regions to work out of the box like.

[DamianSuess]

@dhhunter, Here's an excerpt from the legacy Prism over at Microsoft Patterns and Practices:

Adapter that creates a new Region and binds all the views to the adapted Selector. It also keeps the ActiveViews and the selected items of the Selector in sync.

In the WPF world, the Selector class represents a control that allows a user to select items from among its child elements

For a sample using TabControl, check out my sample repo, Prism.Avalonia Outlookish. The "Mail Module" utilizes the TabControl.

[dhhunter]

In WPF, the TabControl derives from Selector which derives from ItemsControl. In Avalonia, the equivalent to the WPF Selector, seems to be SelectingItemsControl which derives from ItemsControl and is the base class for TabControl...

WPF TabControl
Avalonia SelectingItemsControl

Avalonia.Styling.Selector is used to apply a style to controls...

Avalonia.Styling.Selector

It seems to me that SelectingItemsControl is a better fit for trying to mirror the originals functionality...