public partial class Customer
    {
        public Customer()
        {
            this.Person = new HashSet<Person>();
        }
    
        public int ID { get; set; }
        public string Name { get; set; }
        ...
        public virtual ICollection<Person> Person { get; set; }
    }

public partial class Person
    {
        public Person()
        {
            this.Customer = new HashSet<Customer>();
        }
    
        public int ID { get; set; }
        public string Name { get; set; }
        ...    
        public virtual ICollection<Customer> Customer { get; set; }
    }

public partial class Entities : DbContext
    {
        public Entities()
            : base("name=Entities")
        {			
        }
    
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();
        }    
       
        public virtual DbSet<Customer> Customer { get; set; }       
        public virtual DbSet<Person> Person { get; set; }      
    }

switch (entry.State)
{
case EntityState.Modified:
	entry.State = EntityState.Unchanged;
break;
}

var copyCustomer = repository.context.Customer.Include("Person")
							.AsNoTracking()
							.FirstOrDefault(c => c.ID == 1);