public Customer AddCustomer(Customer customer)
        {
            customer.VismaID = new Random().Next().ToString();

            Console.WriteLine(String.Format("Add Customer: {0}", customer.ToString()));
            return customer;
        }
 public Customer UpdateCustomer(string id, Customer customer)
 {
     Console.WriteLine(string.Format("Update: {0}", customer.ToString()));
     return customer;
 }