如何在Entity Framework代码优先中设置空外键

Question

I have a Order < Customer model.

How do I set this up? When I try to insert a user with a null customerid, it tells me that it cannot be null.

The model is as follows:

public class Order
{
    public long OrderID { get; set; }
    public int CustomerID { get; set; }
    public virtual Customer Customer { get; set; }
    public virtual ICollection<OrderDetail> OrderDetails { get; set; }
}

public partial class Customer
{
    public int CustomerID { get; set; }   
}

In DbContext :

modelBuilder.Entity<Customer>()
            .HasMany(e => e.Orders)
            .WithRequired(e => e.Customer)
            .WillCascadeOnDelete(false);

Answer 1

Have you tried to replace line

.WithRequired(e => e.Customer)

with

.WithOptional(e => e.Customer)

?

And I make the CustomerID property nullable: public int? CustomerID { get; set; }