实体框架中的数据建模和/或查询TPT模型问题

Question

I have an abstract object which have two list of abstract objects in it. The Model is being created and the Database looks fine, but I am unable to make the queries I would expect.

The Data model looks something like this

public abstract class Vehicle
{
    protected Vehicle() 
    {
        this.CrashIncidents = new List<Incident>();
        this.SpeedingIncidents = new List<Incident>();
    }
    [Key]
    public int Id { get; set; }
    public virtual ICollection<Incident> CrashIncidents { get; set; }
    public virtual ICollection<Incident> SpeedingIncidents { get; set; }
}

public class Car : Vehicle
{
    public string Color { get; set; }
}

public class Lorry : Vehicle
{
    public int MaxCarryWeight { get; set; }
}

public abstract class Incident
{
    [Key]
    public int Id { get; set; }
    public virtual ICollection<Incident> VehicleCrashIncidents { get; set; }
    public virtual ICollection<Incident> VehicleSpeedingIncidents { get; set; }
}

public class CrashIncident : Incident
{
    public string Severity { get; set; }
}

public class SpeedingIncident : Incident
{
    public string MPHRegistered { get; set; }
}

Any my OnModelCreating in the Context class looks something like this

modelBuilder.Entity<Vehicle>().HasMany<Incident>(o => o.CrashIncident).WithMany(a => a.VehicleCrashIncidents).Map(m => m.MapLeftKey("Id").MapRightKey("VehicleCrashIncidentId").ToTable("VehicleCrashIncident"));
modelBuilder.Entity<Vehicle>().HasMany<Incident>(o => o.SpeedingIncident).WithMany(a => a.VehicleSpeedingIncidents).Map(m => m.MapLeftKey("Id").MapRightKey("VehicleSpeedingIncidentId").ToTable("VehicleSpeedingIncident"));

modelBuilder.Entity<CrashIncident>().ToTable("CrashIncident");
modelBuilder.Entity<SpeedingIncident>().ToTable("SpeedingIncident");

However I am unable to query things like: Get all Vehicles (or concrete classes) with an Incident of Severity of X ie something like this:

var problems = context.Vehicle.Where(x => x.CrashIncidents.Any(y => y.Severity == "High");

The problem is the last part of the query (in the y-part) where I am not able to select Severity, only the Properties of the Abstract class is visible. I am unable to determine (and thus Google) if the problem lies with my Data model or with my Query.

Answer 1

Inspired by this:

Issue with many-to-many relationship + TPH inhertitance in Entity Framework 6

I got this working. I removed the specific virtual parts from the Abstract part of my model like this:

public abstract class Vehicle
{
    protected Vehicle() 
    {
        this.Incidents= new List<Incident>();
    }
    [Key]
    public int Id { get; set; }
    public virtual ICollection<Incident> Incidents{ get; set; }
}

And changed the navigation properties to

public abstract class Incident
{
    [Key]
    public int Id { get; set; }
    public virtual ICollection<Incident> VehicleIncidents { get; set; }
}

In the OnModelCreating I could remove the two "modelBuilder.Entity().HasMany" lines. In the end I could execute this query:

var problems = context.Vehicle.Where(x => x.Incidents.OfType<CrashIncidents>.Any(y => y.Severity == "High");

I must admit I am unsure of whether I tried that specific query before, so I am not sure if it is the changes in my Data model that allowed me to make that query or it was possible all along and I just didn't know it.