将ListBoxItem的IsSelected属性绑定到该对象的源上的属性

public class Item
{
    public string Name { get; set; }
    public bool IsSelected { get; set; }
}

<ListBox ItemsSource="{Binding Items}">
    <ListBox.ItemTemplate>
        <DataTemplate>
           <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding Name}" />
                <TextBlock Text="{Binding IsSelected}" />
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

public ObservableCollection<Item> Items { get; set; }

<ListBox ItemsSource="{Binding Items}" SelectedItem="{Binding SelectedItem}">
    <ListBox.ItemTemplate>
        <DataTemplate>
           <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding Name}" />
                <TextBlock Text="{Binding IsSelected}" />
            </StackPanel>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>