How to form the correct Code First?

Question

.NET

There are entity classes

class Transaction
    {
        public int ID { get; set; }
        public Customer Customer { get; set; }
        public DateTime Date { get; set; }
        public double Price { get; set; }
        public int Discount { get; set; }
        public double Ended { get; set; }
    }
    class Customer
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public string Last { get; set; }
        public string Other { get; set; }
    }

This model is implemented for the sales application. A purchase is made, for a certain amount, a buyer is sought and through

Transaction trans = new Transaction { Customer = cust, Date = DateTime.Now, Discount = discount, Price = price, Ended = ended };

data is added to the database. Everything works with a bang, but looking at the database, I saw that

How to solve?

Answer 1

Your instance of the Customer class is not tracked by EF. All code is needed. Try using Attach()

Answer 2

add a property to the Customer class
for feedback

Answer 3

public int CustomerID { get; set; }
public virtual Customer Customer { get; set; }