Entity Framework - Code First mapping issue

Question

Is it possible to have a foreign key mapping based on a specific column value.

I have the following entities.

public class Controller
{
    [Key]
    public int Id { get; set; }

    public string Name { get; set; }

    public virtual List<ControllerDevice> ActiveDevices { get; set; }
    public virtual List<ControllerDevice> TamperedDevices { get; set; }
    public virtual List<ControllerDevice> IgnoredDevices { get; set; }
}

public class ControllerDevice
{
    public int Id { get; set; }
    public DeviceStatus Status { get; set; }

    public int ControllerId { get; set; }
    public int NetworkDeviceId { get; set; }

    public virtual Controller Controller { get; set; }
    public virtual NetowkDevice NetowkDevice { get; set; }
}

public class NetowkDevice
{
    [Key]
    public int Id { get; set; }
    public string Name { get; set; }
}

public enum DeviceStatus
{
    Active,
    Tampered,
    Ignored
}

Is it possible to have the ActiveDevices , TamperedDevices and IngoredDevices list be auto populated based on ControllerDevice DeviceStatus , or would I have to create three different tables for each list. IE ActiveControllerDevice , TamperedControllerDevices and IgnoredControllerDevices .

Please let me know if you require further explanation.

Answer 1

Use single devices collection:

public class Controller
{
    [Key]
    public int Id { get; set; }

    public string Name { get; set; }

    public virtual List<ControllerDevice> Devices { get; set; }
}

...and filter it, when you need to process or display devices with specific Status value:

controller.Devices.Where(d => d.Status == DeviceStatus.Active);

Several tables for each devices status, and/or devices hierarchy (theoretically, you can solve this problem with a TPH inheritance) is a way to hell, because instead of single entity ControllerDevice with a status you'll get three entity types ( ActiveControllerDevice , TamperedControllerDevice and IgnoredControllerDevice ), which is not corresponding to model.

Instead of changing status, the device will change its type , and you cannot do that in simple way.

Answer 2

Yes, you can do that. Enum support was introduced in Entity Framework 5, .Net Framework 4.5. In Entity Framework, an enumeration can have the following underlying types: Byte, Int16, Int32, Int64 , or SByte.

And you can filter like this:

context.ControllerDevices.Where(d => d.Status == DeviceStatus.Active);

More here: http://msdn.microsoft.com/en-us/data/hh859576.aspx

Answer 3

public class TestContext : DbContext
{
   public TestContext()
   {
      Configuration.AutoDetectChangesEnabled = true;
      Configuration.LazyLoadingEnabled = true;
      Configuration.ProxyCreationEnabled = true;
      Configuration.ValidateOnSaveEnabled = true;
   }

   public virtual DbSet<NetowkDevice> NetowkDevices{ get; set; }
   public virtual DbSet<ControllerDevice> ControllerDevices{ get; set; }
   public virtual DbSet<Controller> Controlleres{ get; set; }
}

http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/d0443029-2175-4bde-a834-4f8dbf313201/

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