public void OpenOrganizationWindow()
{
    var vm = new OrganizationViewModel(App.Container);

    var view = new OrganizationWindow();
    view.Owner = ActiveWindow;            
    view.DataContext = vm;
    view.Activated += (a, b) => { vm.Load(); };
    view.Closed += (a, b) => { vm.Dispose(); Application.Current.MainWindow.Focus(); };
    view.Show();
}

public void OpenOrganizationWindow()
{
    OrganizationViewModel vm = null;
            
    var view = new OrganizationWindow();
    view.Owner = ActiveWindow;
    view.Dispatcher.BeginInvoke(DispatcherPriority.Background, new Action(() =>
    {
        vm = new OrganizationViewModel(App.Container);
        vm.Load();

        view.DataContext = vm;
        view.Closed += (a, b) => { vm.Dispose(); Application.Current.MainWindow.Focus(); };
    }));
                        
    view.Show();
}

public class EmployeesViewModel : ViewModelBase
{
    private IUnityContainer Container;

    public EmployeesViewModel(IUnityContainer container)
    {
        Container = container;
    }

    public override void Load()
    {
        base.Load();
        Find();
    }

    public void Find()
    {
        var items = Enumerable.Empty<Employee>();

        if (!string.IsNullOrEmpty(LastName))
        {
            var ctx = Container.Resolve<IDataContext>();
            items = ctx.GetEmployees().Where(d => d.LastName.Contains(LastName));
            ctx.Dispose();
        }

        Employees = new ObservableCollection<Employee>(items);
        TotalRows = Employees.Count;        
    }
}