Deleting records from look up table not working in .NET Core 6

I recently upgraded my project to .NET Core 6 and now removing records from my look up tables is not working. I have a Risk object that has a collection of Users. Removing users from the risk object no longer works. Any ideas what I'm doing wrong?

My lookup table is called RiskItemUser, and it has two columns, RiskItemId and UserId.

Code:

 var postSavedRisk = _riskService.Queryable().Include(c => c.AssignedTo).Where(w => w.Id == riskitem.Id).FirstOrDefault();
       
 List<User> usersToRemove = postSavedRisk.AssignedTo.Where(c => userNamesToRemove.Contains(c.UserName)).ToList();
          
using (var db = new ApplicationDbContext())
{
    var postSavedAssginedTo = db.RiskItemUser
                                .Where(w => w.RiskItemId == riskitem.Id)
                                .ToList();

    foreach (var userToRemove in usersToRemove)
    {
        foreach (var riskAssignedTo in postSavedAssginedTo)
        {
            if(userToRemove.Id == riskAssignedTo.UserId)
                db.RiskItemUser.Remove(riskAssignedTo);

            await db.SaveChangesAsync().ConfigureAwait(false);
        }
    }
}

The code, as you show it, looks like it should work, although some parts are hidden. Therefore, it's hard to tell how to make it work. But there's room for simplification, which should result in working code.

You want to remove users whose names are specified by userNamesToRemove from a risk that's specified by riskitem.Id. Assuming that there's a navigation property RiskItemUser.User, removing these data could be done by essentially one line of code:

db.RiskItemUser.RemoveRange(
    db.RiskItemUser.Where(ru => ru.RiskItemId == riskitem.Id 
        && userNamesToRemove.Contains(ru.User.Name)));

await db.SaveChangesAsync().ConfigureAwait(false);

You tagged EFC 6, but as of EFC 7.0, there's support for bulk delete (and update) functions, allowing for single-statement deletion of multiple database records:

db.RiskItemUser
    .Where(db.RiskItemUser.Where(ru => ru.RiskItemId == riskitem.Id 
        && userNamesToRemove.Contains(ru.User.Name)))
    .ExecuteDelete();

This will execute one delete statement, whereas the previous method will execute one statement per row.

Note that this bulk method is like executing raw SQL. There's no communication with EF's change tracker and EF can't coordinate the correct order of statements. I think the general advice should be to not mix these bulk methods with regular SaveChanges calls.