使用DBContext ChangeTracker编写基于事件的SignalR Notification Service - 关注点分离

Question

我有一个控制器，可以修改日历中的约会。我想使用我的SignalR中心通知用户“用户X已更改{appointmentTitle}：列表：{Property} {OriginalValue} {NewValue}”

我是C＃的初学者（语法方面没问题，但是OOP概念是新的）;我正在尝试使用事件来实现上述目标。下面是处理程序和参数，控制器的摘录和我的问题摘要。

代码缩写！

EventArgs的

    public class AppointmentChangeEventArgs : EventArgs
    {
        public EntityState AppointmentState = EntityState.Unchanged;
        public EntityEntry Entity = null;
        public ScheduleData Appointment = null;
    }

事件处理程序

    // maybe this could be just one, and let the consumer decide based on EntityState?
    public EventHandler<AppointmentChangeEventArgs> AppointmentChanged;
    public EventHandler<AppointmentChangeEventArgs> AppointmentAdded;
    public EventHandler<AppointmentChangeEventArgs> AppointmentRemoved;

    protected virtual void OnAppointment(AppointmentChangeEventArgs appointmentChangeEventArgs)
    {
        switch (appointmentChangeEventArgs.AppointmentState)
        {
            case EntityState.Added:
                AppointmentAdded?.Invoke(this, appointmentChangeEventArgs);
                break;
            case EntityState.Deleted:
                AppointmentRemoved?.Invoke(this, appointmentChangeEventArgs);
                break;
            case EntityState.Modified:
                AppointmentChanged?.Invoke(this, appointmentChangeEventArgs);
                break;
            default:
                break;
        }
    }

调节器

public async Task<IActionResult> Batch([FromBody] ScheduleEditParameters param)
    switch (param.Action) {
        case "insert":
             await _dbContext.Appointments.AddAsync(appointment);
             break;
        case "update":
             // .. get Appointment from DB
             appointment.Subject = value.Subject;
             appointment.StartTime = value.StartTime;
             // ...
        case "remove": 
             // .. get Appointment from DB
             _dbContext.Appointments.Remove(appointment);
    }
    var modifiedEntries = _dbContext.ChangeTracker
            .Entries()
            .Where(x => x.State != EntityState.Unchanged && x.State != EntityState.Detached)
            .Select(x => new AppointmentChangeEventArgs() { Entity  = (EntityEntry) x.Entity, AppointmentState = x.State, Appointment = appointment })
            .ToList();

        if (modifiedEntries.Any())
        {
            var notificationService = new NotificationService(signalRHub, notificationLogger);
            AppointmentAdded += notificationService.OnAppointmentChanged;
            AppointmentChanged += notificationService.OnAppointmentChanged;
            AppointmentRemoved += notificationService.OnAppointmentChanged;
        }
        await _dbContext.SaveChangesAsync();

问题

在事件参数中使用EntityEntry和EntityState是否可以？
对于每个修改过的Entry，我可以获得_dbContext.Entry(modifiedEntry).Properties.Where(x => x.IsModified).ToList(); - 但这是否属于NotificationService类？为了做到这一点，我还需要将DbContext传递给NotificationService。
有没有更简单的方法来实现这一目标？添加和删除处理程序很容易（“用户X已添加|删除...约会{标题}”），但为了找出确切的更改，我必须查看修改后的属性。

如果您能够深入了解如何构建和处理此任务，我将不胜感激。谢谢。