Do we need a property of Customer together with a property of CustomerId in Order model class?

I am very new to Entity Framework and data-based application.

Let the Customer data model class be as follows:

public class Customer
{
    public int CustomerId {get;set;}
    public string Name {get;set;}
    //others properties have been omitted for the sake of simplicity.
}

And the Order data model:

public class Order
{
    public int OrderId {get;set;}
    public int CustomerId {get;set;}
    public Customer Customer {get;set;}
    // other properties have been omitted for the sake of simplic开发者_运维百科ity.
}

My question is: "Do we need a property of Customer together with a property of CustomerId in Order model class?"

No, you don't. The Customer object in Order class is sufficient to identify the customer ID. Further, you might want a collection of orders in Customer class, so that you know how many orders the customer has easily, something like this:-

public class Customer {
  private Long customerId;
  private String name;
  private Set<Order> orders = new HashSet<Order>();

  // ... getters/setters 
}

public class Order {
  private Long orderId;
  private Customer customer;

  // ... getters/setters
}

So, if you want to retrieve the customer ID from an order, you will do something like this:-

order.getCustomer().getCustomerId();