Сохранение в базу данных

У меня возникла проблема с сохранением значения отношения «один ко многим» в базе данных. Постоянно пишет, что GroupId отслеживается дважды, но у меня даже в репозитории отслеживания нет.

Если вы каким-либо образом можете помочь оптимизировать код, я буду очень признателен, но если нет или не можете, это тоже нормально.

DepartmentController:

[HttpGet]
public async Task<IActionResult> Details (string id)
{
    var department = await _repository.GetByIdAsync(id);

    if (department != null) 
    {
        var deparment = new EditDepartmentViewModel()
        {
            DepartmentId = department.DepartmentId,
            DepartmentName = department.DepartmentName,
            PeopleInDepartment = _repository.GetNamesByDepartment(id),
        };

        return View(deparment);
    }
    return RedirectToAction("Index");
}

[HttpPost]
public async Task<IActionResult> Details(EditDepartmentViewModel model)
{
    model.DepartmentId = await _repository.GetIdByNameAsync(model.DepartmentName);
    model.Persons = _repository.PersonsInDep(model.DepartmentId);

    var userId = _contextAccessor.HttpContext.User.FindFirstValue(ClaimTypes.NameIdentifier);

    var user = await _userRepository.GetByIdAsync(userId);

    var department = await _repository.GetByIdAsync(model.DepartmentId);

    if (department != null)
    {
        department.DepartmentName = model.DepartmentName;
        department.Persons = model.Persons;

        if (!string.IsNullOrWhiteSpace(model.PeopleInDepartment))
        {
            var names = model.PeopleInDepartment.Split(new[] { ", " }, StringSplitOptions.RemoveEmptyEntries);
            var alreadyin = _repository.GetNamesByDepartment(model.DepartmentId);
            var alinasList = alreadyin.Split(new[] { ", " }, StringSplitOptions.RemoveEmptyEntries);

            if (names.Count() >= alinasList.Count())
            {
                foreach (var name in names)
                {
                    if (alreadyin.Contains(name) == false)
                    {
                        var person = new Person
                        {
                            PersonId = Guid.NewGuid().ToString(),
                            Name = name.Trim(),
                            DepartmentId = department.DepartmentId,
                            GroupPerDay = new List<PersonInGroupPerDay>(),
                        };

                        var dg = new DayGroup()
                        {
                            Id = Guid.NewGuid().ToString(),
                            Group = await _groupRepository.GetByDepartment(department),
                        };

                        var p = new PersonInGroupPerDay()
                        {
                            Id = Guid.NewGuid().ToString(),
                            Person = person,
                            DayGroup = dg,
                            Groups = new List<Group>(),
                        };

                        p.Groups.Add(dg.Group);
                        person.GroupPerDay.Add(p);
                        department.Persons.Add(person);
                    }

                    _repository.Update(department);
                }
            }
            else
            {
                foreach(var name in alinasList)
                {
                    if (model.PeopleInDepartment.Contains(name) == false)
                    {
                        var person = await _repository.GetByNameAsync(name);

                        if (person != null)
                        {
                            var ps = await _repository.GetByPerson(person);

                            foreach (var p in ps)
                            {
                                _repository.DeletePIGPD(p);
                            }

                            _repository.DeletePerson(person);
                        }
                    }

                    _repository.Update(department);
                }
            }
        }

        return RedirectToAction("Index");
    }

    return RedirectToAction("Index");
}

DepartmentRepository:

public bool Save()
{
     var saved = _context.SaveChanges();
     return saved > 0;
}

public bool Update(Department department)
{
     _context.Update(department);
     return Save();
}

public async Task<Department> GetByIdAsync(string id)
{
    var dep = new Department();
    dep.DepartmentId = id;
    dep.DepartmentName = await _context.Departments.AsNoTracking().Where(d => d.DepartmentId == id).Select(d => d.DepartmentName).FirstOrDefaultAsync();
    dep.Persons = await _context.Departments.AsNoTracking().Where(d => d.DepartmentId == id).Select(p => p.Persons).FirstOrDefaultAsync();
    dep.Users = await _context.Departments.AsNoTracking().Where(d => d.DepartmentId == id).Select(d => d.Users).FirstOrDefaultAsync();
    dep.DayDepartments = await _context.Departments.AsNoTracking().Where(d => d.DepartmentId == id).Select(d => d.DayDepartments).FirstOrDefaultAsync();
    dep.Group = await _context.Departments.AsNoTracking().Where(d => d.DepartmentId == id).Select(d => d.Group).FirstOrDefaultAsync();
    dep.Days = await _context.Departments.AsNoTracking().Where(d => d.DepartmentId == id).Select(d => d.Days).FirstOrDefaultAsync();
    dep.Months = await _context.Departments.AsNoTracking().Where(d => d.DepartmentId == id).Select(d => d.Months).FirstOrDefaultAsync();
    return dep;
}

Детали отдела:

@model QLAnCaRedo.Web.ViewModels.EditDepartmentViewModel
<div class = "container mb-3">
    <div class = "row pt-4">
        <div class = "col-6">
            <h2 class = "text-primaary">
                Edit phòng ban
            </h2>
        </div>
    </div>
</div>
<form method = "post" action = "Details">
    <div class = "mb-3">
        <label for = "" class = "form-label">Tên phòng ban</label>
        <input type = "text" class = "form-control" asp-for = "DepartmentName" />
    </div>
    <div class = "mb-3">
        <label for = "" class = "form-label">Người trong phòng ban</label>
        <input type = "text" class = "form-control" asp-for = "@Model.PeopleInDepartment" />
    </div>
    <button type = "submit" class = "btn btn-primary">Submit</button>
    <a type = "button" class = "btn btn-danger" asp-controller = "Department" asp-action = "Delete" asp-route-id = "@Model.DepartmentId">
        Delete
    </a>

Модели

public class Department
{
    [Key]
    public string DepartmentId { get; set; }
    public string DepartmentName { get; set; }
    public List<Person> Persons { get; set; }
    public Group Group { get; set; }
}

public class Group
{
    [Key]
    public string GroupId { get; set; }
    [Required]
    public AppUser AppUser { get; set; }
    public Department Department { get; set; }
    [Required]
    public List<DayGroup> DayGroups { get; set; }
}

public class DayGroup
{
    public string Id { get; set; }
    public DateTime SubcriptionDate { get; set; }
    public Group Group { get; set; }
    public List<PersonInGroupPerDay> PersonInGroups { get; set; }
}

public class PersonInGroupPerDay
{
    public string Id { get; set; }
    public DayGroup DayGroup { get; set; }
    public Person Person { get; set; }
    [DefaultValue(0)]
    public int Set1 { get; set; }
    [DefaultValue(0)]
    public int Set2 { get; set; }
    [DefaultValue(0)]
    public int Set3 { get; set; }
    public List<Group> Groups { get; set; }
}

public class EditDepartmentViewModel
{
    public string DepartmentId { get; set; }
    public string DepartmentName { get; set; }
    public string PeopleInDepartment { get; set; }
    public List<Person> Persons { get; set; }
}