public Customer InsertCustomer(Customer cust) { if (!_Customers.Any(c => c.ID == cust.ID)) { _Customers.Add(cust); return cust; } return null; }
public bool UpdateCustomer(Customer cust) { var targetCust = _Customers.Where(c => c.ID == cust.ID).SingleOrDefault(); if (targetCust != null) { _Customers.Remove(targetCust); _Customers.Add(cust); return true; } return false; }