Insert UUID

[RuslanM1102]

So, I have those tables in my database

and Classes in C#

    [Table("users")]
    public class User : BaseModel
    {
        [PrimaryKey("id")]
        public string Id { get; set; }
        [Column("nickname")]
        public string Nickname { get; set; }
        [Column("image_url")]
        public string ImageUrl { get; set; }
    }
    [Table("Groups")]

  public class Group : BaseModel
  {
      [PrimaryKey("id")]
      public int Id { get; set; }
      [Column("name")]
      public string Name { get; set; }
      [Column("password")]
      public string Password { get; set; }
  }
  
  [Table("users_groups")]
  public class UserGroup : BaseModel
  {
      [PrimaryKey("user_id")]
      public string UserId { get; set; }
      [PrimaryKey("group_id")]
      public int GroupId { get; set; }
      [Column("is_owner")]
      public bool IsOwner { get; set; }
      [Column("nickname")]
      public string Nickname { get; set; }
  }
    

But when I try to insert new row in "users_groups" this way:

var id = int.Parse(Id);
var response = await _client.From<Group>().Where(x => x.Id == id).Get();
if (response.Model != null && response.Model.Password == Password)
{
    var group = new UserGroup();
    group.UserId = _client.Auth.CurrentUser!.Id!;
    group.GroupId = response.Model.Id;
    group.IsOwner = false;
    await _client.From<UserGroup>().Insert(group);
    OnJoined?.Invoke();
}

I'm getting this error

null value in column "user_id" of relation "users_groups" violates not-null constraint

Also, user_id is not null in C#

[acupofjose]

By default PrimaryKey expects to be inserted or generated by the Database, so postgrest-csharp ignores the PrimaryKey value on inserts and updates unless otherwise specified.

If you're going to be inserting the primary key (as you would in your join table) you should just specify PrimaryKey like so:

  [Table("users_groups")]
  public class UserGroup : BaseModel
  {
      [PrimaryKey("user_id", shouldInsert: true)]
      public string UserId { get; set; }
      [PrimaryKey("group_id", shouldInsert: true)]
      public int GroupId { get; set; }
      [Column("is_owner")]
      public bool IsOwner { get; set; }
      [Column("nickname")]
      public string Nickname { get; set; }
  }