ICollection doesn't show up on ASP.NET core web api get request

I have 2 models for a chat system like the following

a chat message model :

    public partial class ChatMessage : BaseEntity
    {
        [ForeignKey("ChatThread")]
        public long ChatThreadID { get; set; }
        public string Sender { get; set; }
        public string Message { get; set; }

    }

and a chat thread model :

    public partial class ChatThread : BaseEntity
    {
        public string User1 { get; set; }
        public string User2 { get; set; }
        [ForeignKey("ChatThreadID")]
        public ICollection<ChatMessage> ChatMessages { get; set; }
    }

I’m doing a simple get request like this to get all the chat threads :

        // GET: api/Chat
        [HttpGet]
        public async Task<ActionResult<IEnumerable<ChatThread>>> GetThreads()
        {
            var threads = _context.ChatThreads.Where(thread => thread.User1 == UserId || thread.User2 == UserId);
            return await threads.ToListAsync();
        }

but the response I’m getting is this although I’m 100% sure that the chat thread has Chat messages in it

[
  {
    "user1": "2",
    "user2": "1",
    "chatMessages": null,
    "id": 1
  }
]

the chatMessages list is always null in the response, I’m fairly new to asp.net, Am I doing the request wrong ?

>Solution :

Relationships won’t be loaded automatically, you need to include them.

[HttpGet]
public async Task<ActionResult<IEnumerable<ChatThread>>> GetThreads()
{
    var threads = _context.ChatThreads.Where(thread => thread.User1 == UserId || thread.User2 == UserId).Include(t => t.ChatMessages);
    return await threads.ToListAsync();
}

Unlike EF6, EF core disables lazy loading by default.
You can find more detailsin the documentation.