Get selected items from collection - multiselect listboxes

See more:

C#

WPF

ListBox

MVVM

Hi,
I have 3 ListBoxes in my app.
ListBox_01

ItemsSource="{Binding EmployeeViewM.MainActivity}"

EmployeeViewM is a ViewModel defined in ViewModelLocator using Ioc.
MainActivity is a ObservableCollection bind to the Model - table with activities via EntityFramework.
- SelectionMode = "Multiple"
- Limit to selected items set to 2

<i:Interaction.Behaviors>
   <listb:ListBoxSelectedItemBehavior SelectedItems="{Binding EmployeeViewM.SelectedAll, Mode=TwoWay}"/>
   <limit:LimitSelectionBehavior Limit="2"/>
</i:Interaction.Behaviors>

- listb:ListBoxSelectedItemBehavior is an attached property to enable SelectedItems from ListBox

public static readonly DependencyProperty SelectedItemsProperty = DependencyProperty.Register("SelectedItems", typeof(ObservableCollection<object>), typeof(ListBoxSelectedItemBehavior), new PropertyMetadata(new ObservableCollection<object>(), PropertyChangedCallback));

- SelectedAll is a property on EmployeeViewM ViewModel for SelectedItems (IList):

private IList _selectedAll = new ArrayList();
public IList SelectedAll {
	get { return _selectedAll; }
	set {
		_selectedAll = value;
		RaisePropertyChanged("SelectedAll");
	}
}

ListBox_02 is the same like ListBox_01, the only difference is that it is bind to another table (NonProcess)

Employees are able to select items on both - max 2 items per ListBox.

All selected items will be visible in ListBox_03.

ItemsSource="{Binding EmployeeViewM.SelectedAll}"

ItemsSource for this ListBox is SelectedAll.

This part works great, but, when employee click on the item in the ListBox_03 I would like to:
- get that selected item name and other attributes from table that it comes from (MainActivity or NonProcess) - best in columns (from IList columns are unknown)
- save that item via .SaveChanges() to another table

What I have tried:

IsSelected - Not able to bind to that property,
ICollection instead IList, ObservableCollection(of Object)