✅ MySQL with Entity Framework, getting null of entity all time

public class UserAssignmentDate
{
    [ForeignKey("UserId")]
    public int UserId { get; set; }

    [ForeignKey("AssignmentId")]
    public int AssignmentId { get; set; }
    
    public DateTimeOffset AssignmentTime { get; set; }
    public DateTimeOffset DeadLineDateTime { get; set; }
    public DateTimeOffset LastUploadDateTime { get; set; }
    public TimeSpan TimeToNextUpload { get; set; }

    // Navigation properties
    public User User { get; set; }
    public Assignment Assignment { get; set; }
}

public class UserAssignmentDate
{
    [ForeignKey("UserId")]
    public int UserId { get; set; }

    [ForeignKey("AssignmentId")]
    public int AssignmentId { get; set; }
    
    public DateTimeOffset AssignmentTime { get; set; }
    public DateTimeOffset DeadLineDateTime { get; set; }
    public DateTimeOffset LastUploadDateTime { get; set; }
    public TimeSpan TimeToNextUpload { get; set; }

    // Navigation properties
    public User User { get; set; }
    public Assignment Assignment { get; set; }
}

            var userAssignmentDate = await dbContext.UserAssignmentDates
                .FirstOrDefaultAsync(userAssignmentDate => userAssignmentDate.UserId == UserId && userAssignmentDate.AssignmentId == assignmentId);

            var userAssignmentDate = await dbContext.UserAssignmentDates
                .FirstOrDefaultAsync(userAssignmentDate => userAssignmentDate.UserId == UserId && userAssignmentDate.AssignmentId == assignmentId);

        foreach (int userId in userIds)
        {
            var userAssignmentDate = new UserAssignmentDate
            {
                UserId = userId,
                AssignmentId = assignmentId,
                AssignmentTime = assignmentTime,
                LastUploadDateTime = DateTimeOffset.MinValue,
            };

            dbContext.UserAssignmentDates.Add(userAssignmentDate);
        }
        
        await dbContext.SaveChangesAsync();

        foreach (int userId in userIds)
        {
            var userAssignmentDate = new UserAssignmentDate
            {
                UserId = userId,
                AssignmentId = assignmentId,
                AssignmentTime = assignmentTime,
                LastUploadDateTime = DateTimeOffset.MinValue,
            };

            dbContext.UserAssignmentDates.Add(userAssignmentDate);
        }
        
        await dbContext.SaveChangesAsync();