Many to Many CRUD operations ASP.Net Core

Question

I have three tables- Contact, Address, and ContactAddress(join table). Here are the tables:

using System;
using System.Collections.Generic;

namespace ProjectWayneAPI.Models
{
public partial class Contact
{

    public Guid Id { get; set; }
    public DateTime? DateEntered { get; set; }
    public bool? Deleted { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; } 
    public string PhoneHome { get; set; }
    public string Email { get; set; }

    public virtual ICollection<ContactAddress> ContactAddress { get; set; }

}
}

using System;
using System.Collections.Generic;

namespace ProjectWayneAPI.Models
{
public partial class Address
{
    public Guid Id { get; set; }
    public DateTime? DateCreated { get; set; }
    public DateTime? DateModified { get; set; }
    public string Lot { get; set; }
    public string Road { get; set; }
    public string Street { get; set; }
    public string Suburb { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string Postcode { get; set; }
    public string Country { get; set; }
    public string Latitude { get; set; }
    public string Longitude { get; set; }
    public bool? Deleted { get; set; }

    public virtual ICollection<ContactAddress> ContactAddress { get; set; }
}
}

using System;
using System.Collections.Generic;

namespace ProjectWayneAPI.Models
{
public partial class ContactAddress
{
    public Guid Id { get; set; }
    public DateTime? Created { get; set; }
    public bool? Deleted { get; set; }
    public Guid? ContactId { get; set; }
    public Guid? AddressId { get; set; }

    public virtual Address Address { get; set; }
    public virtual Contact Contact { get; set; }
}
}

For simplicity, I am not using the Repository Pattern.

For create operation, there are two scenarios:

• Populating ContactAddress table while creating the Contact and Address table
• Populating the Join table after creating both the Contact and Address table

For our business requirement, I am trying to adapt, the first one because the user will populate the contact and address table at the same time while the user hits "save" button.

How do I do that one(populating the linkup entity while creating both the entities.), also how do i update the many to many relationship while updating the entity? And also the delete operation.

Answer 1

If your Guid Id is generated at the database level (it's assigned after insert). for your case: insert Contact and Address , and link them, you have to first insert Contact and Address like this:

var contact = new Contact(); 
var address = new Address();  

dbContext.Add(contact);
dbContext.Add(address);

dbContext.SaveChanges();

var contactAddress = new ContactAddress() 
{
   AddressId = address.Id,
   ContactId = contact.Id 
}
dbContext.Add(contactAddress);
dbContext.SaveChanges();