How to support ListBox SelectedItems binding with MVVM in a navigable application

Try creating an IsSelected property on each of your data items and binding ListBoxItem.IsSelected to that property

<Style TargetType="{x:Type ListBoxItem}">    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" /></Style>

Rachel's solutions works great! But there is one problem I've encountered - if you override the style of ListBoxItem, you loose the original styling applied to it (in my case responsible for highlighting the selected item etc.). You can avoid this by inheriting from the original style:

<Style TargetType="{x:Type ListBoxItem}" BasedOn="{StaticResource {x:Type ListBoxItem}}">    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" /></Style>

Note setting BasedOn (see this answer).

I couldn't get Rachel's solution to work how I wanted it, but I found Sandesh's answer of creating a custom dependency property to work perfectly for me. I just had to write similar code for a ListBox:

public class ListBoxCustom : ListBox{    public ListBoxCustom()    {        SelectionChanged += ListBoxCustom_SelectionChanged;    }    void ListBoxCustom_SelectionChanged(object sender, SelectionChangedEventArgs e)    {        SelectedItemsList = SelectedItems;    }    public IList SelectedItemsList    {        get { return (IList)GetValue(SelectedItemsListProperty); }        set { SetValue(SelectedItemsListProperty, value); }    }    public static readonly DependencyProperty SelectedItemsListProperty =       DependencyProperty.Register(nameof(SelectedItemsList), typeof(IList), typeof(ListBoxCustom), new PropertyMetadata(null));}

In my View Model I just referenced that property to get my selected list.