Many-to-many self referencing relationship

by

The post you are following is definitely wrong.

Every collection or reference navigation property can only be a part of a single relationship. While many to many relationship with explicit join entity is implemented with two one to many relationships. The join entity contains two reference navigation properties, but the main entity has only single collection navigation property, which has to be associated with one of them, but not with both.

One way to resolve the issue is to add a second collection navigation property: 

public class WordEntity
{
    public long Id { get; set; }
    public string Name { get; set; }
    public string Json { get; set; }

    public virtual List<WordSinonymEntity> Sinonyms { get; set; }
    public virtual List<WordSinonymEntity> SinonymOf { get; set; } // <--
}

and specify the associations via fluent API:

modelBuilder.Entity<WordSinonymEntity>()
     .HasOne(pt => pt.Sinonym)
     .WithMany(p => p.SinonymOf) // <--
     .HasForeignKey(pt => pt.SinonymId)
     .OnDelete(DeleteBehavior.Restrict); // see the note at the end

modelBuilder.Entity<WordSinonymEntity>()
    .HasOne(pt => pt.Word)
    .WithMany(t => t.Sinonyms)
    .HasForeignKey(pt => pt.WordId);

Another way is to leave the model as is, but map the WordSinonymEntity.Sinonym to unidirectional association (with refeference navigation property and no corresponding collection navigation property):

modelBuilder.Entity<WordSinonymEntity>()
     .HasOne(pt => pt.Sinonym)
     .WithMany() // <--
     .HasForeignKey(pt => pt.SinonymId)
     .OnDelete(DeleteBehavior.Restrict); // see the note at the end

modelBuilder.Entity<WordSinonymEntity>()
    .HasOne(pt => pt.Word)
    .WithMany(t => t.Sinonyms)
    .HasForeignKey(pt => pt.WordId);

Just make sure that WithMany exactly matches the presence/absence of the corresponding navigation property.

Note that in both cases you have to turn the delete cascade off for at least one of the relationships and manually delete the related join entities before deleting the main entity, because self referencing relationships always introduce possible cycles or multiple cascade path issue, preventing the usage of cascade delete.

More Related Contents:

  1. Entering keys manually with Entity Framework
  2. navigation property should be virtual – not required in ef core?
  3. Can I reuse code for selecting a custom DTO object for a child property with EF Core?
  4. Filter all queries (trying to achieve soft delete)
  5. How to add the same column to all entities in EF Core?
  6. Dynamically changing schema in Entity Framework Core
  7. Include with FromSqlRaw and stored procedure in EF Core 3.1
  8. Could not load file or assembly Microsoft.Extensions.DependencyInjection.Abstractions, Version=1.1.0.0
  9. Entity framework EF.Functions.Like vs string.Contains
  10. The LINQ expression could not be translated and will be evaluated locally
  11. Entity Framework | Sequence contains more than one matching element
  12. Unable to edit db entries using EFCore, EntityState.Modified: “Database operation expected to affect 1 row(s) but actually affected 0 row(s).”
  13. Working with SQL views in Entity Framework Core
  14. EF models. Navigation properties can only participate in a single relationship
  15. Implementing recursive property loading in EF Core
  16. How to set Identity Seed value in code-first?
  17. How do I stop Entity Framework from trying to save/insert child objects?
  18. Entity Framework – Code First – Can’t Store List
  19. Pass connection string to code-first DbContext
  20. A specified Include path is not valid. The EntityType does not declare a navigation property with the name *
  21. How to group by on 2 child entities and get total of both this child entities?
  22. DbArithmeticExpression arguments must have a numeric common type
  23. ‘No database provider has been configured for this DbContext’ on SignInManager.PasswordSignInAsync
  24. Enable Migrations with Context in Separate Assembly?
  25. update-database: “A network-related or instance-specific error occurred while establishing a connection to SQL Server”
  26. Better way to query a page of data and get total count in entity framework 4.1?
  27. How to compare only Date without Time in DateTime types?
  28. Calling a SQL User-defined function in a LINQ query
  29. ef core doesn’t use ASPNETCORE_ENVIRONMENT during update-database
  30. Use both AddDbContextFactory() and AddDbContext() extension methods in the same project

Leave a Comment