How to refer two tables, using a column in another table - Entity Framework - asp.net

Question

As per the image above, I have a requirement where, Table C needs to refer both Table A and Table B.
Note: RefId in Table_C is a reference key for both Tables A and B.
Please, refer the code snippets,
Table_A Class
public partial class Table_A
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Table_C> Table_C { get; set; }
}
Table_B Class
public partial class Table_B
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Table_C> Table_C { get; set; }
}
Table_C Class
public partial class Table_C
{
public int Id { get; set; }
public int RefId { get; set; }
public Type Type {get; set; }
public virtual Table_A Table_A { get; set; }
public virtual Table_B Table_B { get; set; }
}
Fluent API
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Table_1>()
.Property(e => e.Name)
.IsFixedLength();
modelBuilder.Entity<Table_1>()
.HasMany(e => e.Table_3)
.WithRequired(e => e.Table_1)
.HasForeignKey(e => e.RefId)
.WillCascadeOnDelete(false);
modelBuilder.Entity<Table_2>()
.Property(e => e.Name)
.IsFixedLength();
modelBuilder.Entity<Table_2>()
.HasMany(e => e.Table_3)
.WithRequired(e => e.Table_2)
.HasForeignKey(e => e.RefId)
.WillCascadeOnDelete(false);
}
However, the below error occurs when trying to achieve this requirement using the code shown above.
The INSERT statement conflicted with the FOREIGN KEY constraint
"FK_dbo.TableC.TableA_Id". The conflict occurred in database "TestDB",
table "dbo.TableA", column 'Id'. The statement has been terminated
How can this be implemented using Entity Framework 6 (SQL Server 2014, .NET framework 4.6.1)?

Answer 1

Seems to work fine for me:
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Data;
using System.Data.Entity;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Ef6Test
{
public partial class Table_A
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Table_C> Table_C { get; } = new HashSet<Table_C>();
}
//Table_B Class
public partial class Table_B
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Table_C> Table_C { get; } = new HashSet<Table_C>();
}
//Table_C Class
public partial class Table_C
{
public int Id { get; set; }
public int RefId { get; set; }
public string Type { get; set; }
public virtual Table_A Table_A { get; set; }
public virtual Table_B Table_B { get; set; }
}
class Db: DbContext
{
public DbSet<Table_A> Table_A { get; set; }
public DbSet<Table_B> Table_B { get; set; }
public DbSet<Table_C> Table_C { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Table_A>()
.HasMany(e => e.Table_C)
.WithRequired(e => e.Table_A)
.HasForeignKey(e => e.RefId)
.WillCascadeOnDelete(false);
modelBuilder.Entity<Table_B>()
.HasMany(e => e.Table_C)
.WithRequired(e => e.Table_B)
.HasForeignKey(e => e.RefId)
.WillCascadeOnDelete(false);
}
}
class Program
{
static void Main(string[] args)
{
Database.SetInitializer(new DropCreateDatabaseAlways<Db>());
using (var db = new Db())
{
db.Database.Log = m => Console.WriteLine(m);
db.Database.Initialize(true);
var a = new Table_A();
var b = new Table_B();
var c = new Table_C();
a.Table_C.Add(c);
b.Table_C.Add(c);
db.Table_A.Add(a);
db.Table_B.Add(b);
db.Table_C.Add(c);
db.SaveChanges();
}
Console.ReadKey();
}
}
}

Answer 2

I managed to fulfill this requirement using the comments made by #David Browne - Microsoft. Therefore, usage of multiple columns to refer multiple related tables is the approach for this sort of a scenario. Hope this will help anyone looking for an answer to a question of this nature. Thanks #David Browne - Microsoft for the valuable input.