OOP：仅在数据访问层中使用实体框架

Question

My application has a business logic layer, and a data access layer. I want to give only the data access layer access to the database model. Now, I can easily do this, but then my UI classes cannot access the database classes like Reminder :

namespace Database
{
    using System;
    using System.Collections.Generic;

    public partial class Reminder
    {
        public long Id { get; set; }
        public string Name { get; set; }
        public string Date { get; set; }
        public string RepeatType { get; set; }
        public string Note { get; set; }
        public long Enabled { get; set; }
        public string SoundFilePath { get; set; }
        public string PostponeDate { get; set; }
        public Nullable<long> EveryXCustom { get; set; }
        public string RepeatDays { get; set; }
        public Nullable<long> DayOfMonth { get; set; }
    }
}

which is inside the database class library

I use this reminder class to store reminders. In my UI classes I use this class for various reasons.

To make use of this Reminder class, I simply add a reference to the class library that needs to use it. This works fine, but the problem is that every class library that references this, can alter the database like this.

If I'm not using Entity Framework, I could simply have a Reminder class outside the model (because there is no model) and load reminders from the database into that and extract them without using Entity Framework.

Here's an example of why I need to use the Reminder class in my UI classes (this is just a small code sample of one UI class)

This code is inside a timer that ticks every 30 seconds

// We will check for reminders here every 30 seconds.
foreach (Reminder rem in BLReminder.GetReminders())
{
    // Create the popup. Do the other stuff afterwards.
    if(rem.PostponeDate != null && Convert.ToDateTime(rem.PostponeDate) <= DateTime.Now && rem.Enabled == 1)
    {
        allowRefreshListview = true;

        // temporarily disable it. When the user postpones the reminder, it will be re-enabled.
        rem.Enabled = 0;
        BLReminder.EditReminder(rem);

        MakePopup(rem);
    }
    else if(Convert.ToDateTime(rem.Date.Split(',')[0]) <= DateTime.Now && rem.PostponeDate == null && rem.Enabled == 1)
    {
        allowRefreshListview = true;

        // temporarily disable it. When the user postpones the reminder, it will be re-enabled.
        rem.Enabled = 0;
        BLReminder.EditReminder(rem);

        MakePopup(rem);
    }
}    

GetReminders will do get the reminders from the database and put them in reminder objects

using (RemindMeDbEntities db = new RemindMeDbEntities())
{                
    localReminders = (from g in db.Reminder select g).ToList();
    db.Dispose();                
}

Answer 1

If im not using the entity framework, i could simply have a reminder class outside the model

You could create an interface instead of a class outside of the model in a shared assembly:

public interface IReminder
{
    public long Id { get; }
    public string Name { get; }
    public string Date { get; }
    public string RepeatType { get; }
    public string Note { get; }
    public long Enabled { get; }
    public string SoundFilePath { get; }
    public string PostponeDate { get; }
    public Nullable<long> EveryXCustom { get; }
    public string RepeatDays { get; }
    public Nullable<long> DayOfMonth { get; }
}

Your Entity can than implement the interface:

public partial class Reminder : IReminder
{
    //...
}

Maybe you want to make your Entities only internal visible and expose public service methods like IEnumerable<IReminder> GetReminders()

Answer 2

You can create separate project called ie Shared and put there all classes which are used in many projects. Then you need to reference this project by UI project and data access project (and by others which use these classes).

Both will have access to shared classes and UI won't be able to call data access layer directly.

You can also create interface outside of data access layer but if your classes are DTOs (Data Transfer Object) first option will be better.