Use a slightly different approach to the one that was previously there: create an item template that contains `DisplayMemberBinding`. This is the approach that WPF broadly uses too.
A lot still broken, in particular virtualization is completely removed.`ItemsPresenter` now no longer has an `Items` or `ItemTemplate` property; it detects when it's hosted in an `ItemsControl`. `IItemsPresenter` interface removed.
`SelectionModel` needs to subscribe to `CollectionChanged` on the items before `ItemsControl` in order for the selection to be correct when we come to setting the selected state.
Because `SelectionModel.Source` isn't subscribed during initialization in `ItemsChanged`, we also need to make sure we don't subscribe `ItemsControl` to the collection changes during initialization. Instead subscribe in `OnInitialized` (this requires a few tests to be rooted in order to be called).
Fixes#4293
Exposing the `ContentPresenter.Child` in `ItemsControl.LogicalChildren` was causing problems when detaching and reattaching an `ItemsControl` to the logical tree. Instead, expose the `ContentPresenter` itself in effect meaning that `ItemsControl` has a "container" type just like the controls derived from it.
Fixes#3487
Added an `IDataTemplateHost` interface with a `IsDataTemplatesInitialized` property to prevent the need for allocating empty `DataTemplates` collections for many controls.
Make the untyped ItemContainerGenerator create `ContentPresenter`
containers when the data isn't a control. This is required for correct
binding to `DataContext` in a data template.
...during ApplyTemplate. This was so that ItemsControls could their find
ItemsPresenters nested in other templated controls. Instead use
IItemsPresenterHost to make the presenter register itself with its
TemplatedParent.
Steven Kirk
Giuseppe Lippolis
Tim
Murdo R Ergeaux
Steven Kirk
adospace
Nikita Tsukanov
Jeremy Koritzinsky
Dan Walmsley