public MultiSelectionVM(
     MultiSelectionVMDescriptor <TItemSource> descriptor,
     IServiceLocator serviceLocator
     )
     : base(descriptor, serviceLocator)
 {
 }
 internal MultiSelectionBaseVM(
     MultiSelectionVMDescriptor <TItemSource, TItemVM> descriptor,
     IServiceLocator serviceLocator
     )
     : base(descriptor, serviceLocator)
 {
     //NonExistingSelectedSourceItems = new List<TItemSource>();
 }
 public MultSelectionAccessor(
     MultiSelectionVMDescriptor <TItemSource, SelectableItemVM <TItemSource, TItemVM> > descriptor
     )
 {
     _descriptor = descriptor;
 }