Entity Framework 6 TPT, Multiple collections of same type on parent entity - entity-framework

Question

Is there any way to configure this and get it to work in EF? I'd like to use this scenario if possible, but haven't found any way to do this without getting a the error "The DELETE statement conflicted with the REFERENCE constraint"
I have seen suggestions for handling this using inheritance. Such as in this post... However, is this really not possible to configure using the fluent API?
Multiple collections of same type in entity framework
Here is my test case....
public class ToolSet
{
public int Id { get; set; }
public virtual ICollection<Tool> Tools { get; set; }
}
public class Tool
{
public int Id { get; set; }
public virtual ICollection<Fluid> HeavyFluid { get; set; }
public virtual ICollection<Fluid> LightFluid { get; set; }
}
public class Fluid
{
public int Id { get; set; }
public double Density { get; set; }
}
public class ExampleContext : DbContext
{
public DbSet<ToolSet> ToolSets { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Entity<ToolSet>().HasMany(x => x.Tools).WithRequired().WillCascadeOnDelete(true);
modelBuilder.Entity<Tool>().HasMany(x => x.HeavyFluid).WithOptional().WillCascadeOnDelete(true);
modelBuilder.Entity<Tool>().HasMany(x => x.LightFluid).WithOptional().WillCascadeOnDelete(false);
}
}
public class SeedDb : DropCreateDatabaseAlways<ExampleContext>
{
public override void InitializeDatabase(ExampleContext context)
{
base.InitializeDatabase(context);
var heavyFluids = new List<Fluid> { new Fluid { Density = 1 }, new Fluid { Density = 2 } };
var lightFluids = new List<Fluid> { new Fluid { Density = .1 }, new Fluid { Density = .2 } };
var toolSet = new ToolSet
{
Tools = new List<Tool>
{
new Tool{HeavyFluid =heavyFluids, LightFluid = lightFluids}
}
};
context.ToolSets.Add(toolSet);
context.SaveChanges();
}
}
[TestClass]
public class UnitTest1
{
[TestInitialize]
public void TestInitialize()
{
Database.SetInitializer(new SeedDb());
}
[TestMethod]
public void TestMethod1()
{
using (var a = new ExampleContext())
{
var toRemove = a.ToolSets.First();
a.ToolSets.Remove(toRemove);
a.SaveChanges();
Assert.IsFalse(a.ToolSets.Any());
}
}
}

Answer 1

am not sure if what you are seeking is possible. you want EF To Deferenciate between two collections of the same type,both optional,one with cascading on delete and the other no.
EntityFramework map Fluid to One Table and only one table,this table has some foreign keys columns to represent the relationship with the the Tool.according to your example you will end up having two foreign keys in the same column to the same type(Tool_Id and Tool_Id1 : one of them will be empty at a time).the Fluent Api is a validation Api ,no more no less.so it can't help accomplishing what you want. I think your best friends are enums and Inheritance as in the link you provided (wich i don't understand why you don't want to use them).
one way i can think now, wich i didn't test and i don't either recommand it even if it works. is having some sort of column that can take one of two values, L or H and work around it in your code to deferentiate between Heavy and Light Tools.
what i said now ,is just an opinion and there might be solutions that i don't know about.let's wait and see.