`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
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.
aljosas
Steven Kirk
Steven Kirk
Nikita Tsukanov
Dan Walmsley
Jumar Macato