public IEnumerable<ProductItem> get_products_in(DepartmentItem testdepartment)
 {
     return Enumerable.Range(1, 100).Select(x => new ProductItem {name = x.ToString("Product 0")});
 }
 public IEnumerable<DepartmentItem> get_departments_in(DepartmentItem selected_department)
 {
     return Enumerable.Range(1, 100).Select(x => new DepartmentItem {name = x.ToString("Sub Department 0")});
 }