实体框架核心无法使用Npgsql获取Forein关键实体

Question

I have encountered in a strange behavior of Npgsql for Entity Framework Core:

My Models:

public class Customer
{
    public Customer()
    {
        Numbers = new List<TelephoneNumber>();
        Emails = new List<Email>();
    }
    public int CustomerId { get; set; }
    public string FirstName { get; set; }
    public string SecondName { get; set; }

    public Address Address { get; set; }

    public List<TelephoneNumber> Numbers {get;set;}

    public List<Email> Emails { get; set; }

    public string Note { get; set; }
}

public class Address
{
    public int AddressId { get; set; }
    public string Street { get; set; }
    public int HouseNumber { get; set; }

    public int Code { get; set; }

    public string City { get; set; }

    public int CustomerId { get; set; }
    public Customer Customer { get; set; }
}

public class Email
{
    public int EmailId { get; set; }

    public string Address { get; set; }

    public int CustomerId { get; set; }
    public Customer Customer { get; set; }
}

public class TelephoneNumber
{
    public int TelephoneNumberId { get; set; }

    public string Number { get; set; }

    public int CustomerId { get; set; }
    public Customer Customer { get; set; }
}

And my DbContext:

public class CustomerContext : DbContext
{
    public CustomerContext(DbContextOptions<CustomerContext> options) : base(options)
    {}
    public DbSet<Customer> Customers {get; set;}
    public DbSet<Address> Addresses { get; set; }

    public DbSet<Email> Emails {get;set;}
    public DbSet<TelephoneNumber> Numbers {get;set;}

    protected override void OnModelCreating(ModelBuilder builder)
    {
        builder.Entity<Customer>().HasKey(m => m.CustomerId);
        builder.Entity<Address>().HasKey(m => m.AddressId);
        builder.Entity<Email>().HasKey(m => m.EmailId);
        builder.Entity<TelephoneNumber>().HasKey(m => m.TelephoneNumberId);

        base.OnModelCreating(builder);
    }
}

I have successfully connected to the postgresql database and the schema is created with "dotnet ef migrations add initPG" and "dotnet ef database update" without problems with right forein key constrains-etc..

Then i create a customer with:

var created = _context.Customers.Add(cust);
_context.SaveChanges();

With customer containing a address,email and telephone number.

My problem is when i want to get all customers from the DB with:

IEnumerable<Customer> customers = _context.Customers.ToList();

I only get a Customers with empty Address, Email and TelephoneNumber properties!!

Do i have a logical misunderstanding here!? I would think the EF-Framework does the table joins automatically. Or do i manually need to get this seperate elements from the customer by myself?

At several sources i see the include keyword to get the forein-key properties but my IDE shows that the DbContext has no include method at all!

Answer 1

if you want the include extension methods, type

using System.Data.Entity;

Or, if using EF 7, as per rubiktubik 's suggestion

using Microsoft.EntityFrameworkCore

at the top of your file

at that point, you should be able to do

IEnumerable<Customer> customers = _context.Customers
    .Include(c => c.Emails)
    .ToList();