//MyHelpers.cshtml:
//Recursive function for rendering child nodes for the specified node

@helper CreateNavigation(int parentId, int depthNavigation, int currentPageId)
{
   @MyHelpers.Navigation(parentId, depthNavigation, currentPageId);
}

@helper Navigation(int parentId, int depthNavigation, int currentPageId)
{

   if ()
   {
       if ()
       {
         <ul style="">
            @foreach ()
            {
               if ()
                {
                   <li class="">
                      @Navigation(child.Id, depthNavigation, currentPageId)
                   </li>
                }
             }
         </ul>
      }
   }
}

//I call the method in _Menu.cshtml:
 @MyHelpers.CreateNavigation(rootNode.Id, 2,currentPageId);

public class TaskEditingBusinessEventHandler : BusinessEventHandler<EditingBusinessEvent<TaskModel, int>>
{
    private readonly ILogger<TaskEditingBusinessEventHandler> _logger;

    public TaskEditingBusinessEventHandler(ILogger<TaskEditingBusinessEventHandler> logger)
    {
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    public override Task<Result> Handle(EditingBusinessEvent<TaskModel, int> @event)
    {
        foreach (var model in @event.Models)
        {
            _logger.LogInformation($"Title changed from: {model.OriginalValue.Title} to: {model.NewValue.Title}");
        }

        return Task.FromResult(Ok());
    }
}

public class ModifiedModel<TValue>
{
    public TValue NewValue { get; set; }
    public TValue OriginalValue { get; set; }
}

OOP : Everything is an object
CRUD-based thinking : Everything is CRUD

public class ItemCategoryCreatedBusinessEventHandler : IBusinessEventHandler<CreatedBusinessEvent<ItemCategoryModel, int>>
{
    private readonly ISaleMethodService _saleMethodService;

    public TaskEditingBusinessEventHandler(ISaleMethodService saleMethodService)
    {
        _saleMethodService = saleMethodService ?? throw new ArgumentNullException(nameof(saleMethodService));
    }

    public override Task<Result> Handle(CreatedBusinessEvent<ItemCategoryModel, int> @event)
    {
        var methods = _saleMethodService.FindAsnc();

        foreach (var method in methods)
        {
            foreach (var model in @event.Models)
            {
                method.ItemCategories.Add(new SaleMethodItemCategoryModel
                {
                    ItemCategoryId = model.Id,
                    TrackingState = TrackingState.Added;
            });
        }
    }

     return _saleMethodService.EditAsync(methods);
}