Update Statement Deleting Navigation Property Records - postgresql

Question

I'm using EF Core to add new games to a Sudoku API I'm building. Each game has one user who can have many roles. Whenever I add a new game I have to manually pull the users roles and add them back to the context otherwise they are lost. Likewise, as I'm adding new games there are situations where all other prior games for the user are lost. What am I doing wrong?
I've tried
_context.Games.Add(game);
which caused it's own set of issues, I then tried
_context.Games.Update(game);
but I'm getting the current issue:
public async Task<Game> CreateGame(CreateGameRO createGameRO) {
var userActionResult =
await _userService.GetUser(createGameRO.UserId);
var difficultyActionResult =
await _difficultiesService.GetDifficulty(createGameRO.DifficultyId);
SudokuMatrix matrix = new SudokuMatrix();
matrix.GenerateSolution();
Game game = new Game(
userActionResult.Value,
matrix,
difficultyActionResult.Value);
// EF Core loses reference to the users roles when creating new games.
// Before we save the new game we pull a reference to the users roles...
var user = game.User;
var userRoles = _context.UsersRoles.Where(u => u.UserId == user.Id).ToList();
//var userGames = _context.Games.Where(g => g.UserId == user.Id).ToList();
_context.Games.Update(game);
await _context.SaveChangesAsync();
// ...then we reattach the users roles to the data context.
_context.UsersRoles.AddRange(userRoles);
//_context.Games.AddRange(userGames);
await _context.SaveChangesAsync();
return game;
}
I added logging to my app and noted the following generated SQL commands:
DELETE FROM "Games"
WHERE "Id" = #p0;
DELETE FROM "Games"
WHERE "Id" = #p1;
DELETE FROM "SudokuCells"
WHERE "Id" = #p2;
DELETE FROM "SudokuCells"
WHERE "Id" = #p3;
DELETE FROM "SudokuCells"
WHERE "Id" = #p4;
The situations where this happens is as follows... suppose I make a user Dean Winchester and then add a second user Sam Winchester. I then create two new games for Dean and everything is fine, I create two new games for Sam and everything is still fine... I then create another game for Dean and the above SQL is created and the first two games are deleted.

Answer 1

Since no one else can answer this I'm going to go ahead and do so.
Supposedly I'm working in a disconnected environment with a WebAPI where the context doesn't know about the other games and roles my users have unless I specifically track them. However, I have documented evidence in my log where EF core is going out of it's way to track down the users games and roles... and deletes them!
This behavior makes no sense to me and I'd appreciate it if someone could explain the underlying logic for handling it this way. To me it is counter intuitive that an update statement is encapsulating deletes.
My solution now looks like this:
Game game = new Game(
userActionResult.Value,
matrix,
difficultyActionResult.Value);
var user = await _context.Users
.FirstOrDefaultAsync(u => u.Id == userActionResult.Value.Id);
var userRoles = await _context.UsersRoles
.Where(ur => ur.UserId == user.Id)
.ToListAsync();
var userGames = await _context.Games
.Where(g => g.UserId == user.Id)
.ToListAsync();
_context.Games.Update(game);
await _context.SaveChangesAsync();
_context.UsersRoles.AddRange(userRoles);
await _context.SaveChangesAsync();
_context.Games.UpdateRange(userGames);
await _context.SaveChangesAsync();
I have to make three trips to the database to protect the data I didn't want touched in the first place... this is stupid but it works.
I'm not happy with this solution. Suppose a user had 1000 games? I have to pull all 1000 games into memory... add my new game... EF core then deletes all prior 1000 games... then I have to re add the 1000 games?