These are chat archives for AvaloniaUI/Avalonia
TextBox's visual descendants
textBox.GetVisualDescendents().OfType<ScrollViewer>().First()should give you that
treeView.GetObservable(TreeView.SelectedItemProperty)which will give you an observable which will be fired with the initial value of the selected item and the new value each time it changes
MessageBox. we've still not got those yet!