private void FilterCostAccounts() { FilteredCostAccounts.Clear(); if (SelectedCategory.IsNull()) { return; } List <int> ids = GetChildIds(SelectedCategory.CostAccountCategoryId).ToList(); if (ids.IsNull()) { return; } ids.Add(SelectedCategory.CostAccountCategoryId); FilteredCostAccounts.AddRange(_CostAccounts.Where(x => ids.Contains(x.RefCostAccountCategoryId))); }