How to update multiple tables in ASP.NET using edit view and controller

public class UserViewModel
{
    public int Id { get; set; }
    public string EmailAddress { get; set; }
    public string Username { get; set; }
    public List<UserRoleViewModel> Roles { get; set; }
}

public class UserRoleViewModel
{
    public int RoleId { get; set; }
    public string RoleName { get; set; }
    public bool IsSelected { get; set; }
}

private void PopulateRoles(UserViewModel model)
{
    // Load all of the role names from the database:
    DataTable allRoles = ListAllRolesFromDatabase();
    
    // Convert the roles to the view-model:
    var roles = allRoles.AsEnumerable()
        .Select(r => new UserRoleViewModel 
        { 
            RoleId = r.Field<int>("Id"), 
            RoleName = r.Field<string>("Name") 
        })
        .ToDictionary(r => r.RoleId);
    
    if (model.Roles != null)
    {
        // We've posted back to the server - take the selected roles from the form:
        foreach (var role in model.Roles.Where(r => r.IsSelected))
        {
            if (roles.TryGetValue(role.RoleId, out var vm))
            {
                vm.IsSelected = true;
            }
        }
    }
    else if (model.Id != 0)
    {
        // We're editing an existing user - load their roles from the database:
        DataTable currentRoles = LoadRolesForUserFromDatabase(model.Id);
        foreach (DataRow row in currentRoles.Rows)
        {
            int id = row.Field<int>("Id");
            if (roles.TryGetValue(id, out var vm))
            {
                vm.IsSelected = true;
            }
        }
    }
    
    // Set the roles on the view-model:
    model.Roles = roles.Values.ToList();
}

[HttpGet]
public ActionResult Add()
{
    var model = new UserViewModel();
    PopulateRoles(model);
    return View(model);
}

[HttpPost, ValidateAntiForgeryToken]
public ActionResult Add(UserViewModel model)
{
    if (!ModelState.IsValid)
    {
        PopulateRoles(model);
        return View(model);
    }
    
    CreateUserAndAssignRolesInDatabase(model);
    return RedirectToAction(nameof(Index));
}

[HttpGet]
public ActionResult Edit(int id)
{
    DataRow row = LoadUserDetailsFromDatabase(id);
    if (row is null) return RedirectToAction(nameof(Index));
    
    var model = new UserViewModel
    {
        Id = row.Field<int>("Id"),
        EmailAddress = row.Field<string>("Email"),
        Username = row.Field<string>("Username"),
    };
    
    PopulateRoles(model);
    return View(model);
}

[HttpPost, ValidateAntiForgeryToken]
public ActionResult Edit(UserViewModel model)
{
    if (!ModelState.IsValid)
    {
        PopulateRoles(model);
        return View(model);
    }
    
    UpdateUserAndRolesInDatabase(model);
    return RedirectToAction(nameof(Index));
}

<div class="form-group row">
    <label class="col-form-label col-sm-3">Roles</label>
    <div class="col-sm">
        <ul class="list-unstyled">
        @for (int index = 0; index < Model.Roles.Count; index++)
        {
            <li>
                <div class="form-check mt-2">
                    @Html.HiddenFor(m => m.Roles[index].RoleId)
                    @Html.CheckBoxFor(m => m.Roles[index].IsSelected, new { @class = "form-check-input" })
                    @Html.LabelFor(m => m.Roles[index].IsSelected, Model.Roles[index].RoleName)
                </div>
            </li>
        }
        </ul>
    </div>
</div>