private void DepartmentsTree_SelectionChanged(object sender, EventArgs _)
{
TreeNode node = DepartmentsTree.SelectedNode;
Employee[] emps = ((node != null ? (Employee[])Tree.GetTreeNodeData(node) : null) ?? new Employee[0]);
EmployeesGrid.BeginRebuild();
foreach (Employee e in emps)
{
EmployeesGrid.AddItem(GetGridTexts(e), e);
}
EmployeesGrid.AddItem(GetGridTexts(null), null);
EmployeesGrid.EndRebuild();
}