EF models. Navigation properties can only participate in a single relationship

by

You can’t reuse Team.Games as the inverse property for both Game.FirstTeam and Team.SecondTeam. Think of it, if you add game to Team.Games, how would EF know which team it is, first or second?

You need two collections to describe the relationships. And that’s also a chance to add some more meaning to the class model. For example (only modified code):

public class Game
{
    ...
    public int HomeTeamId { get; set; }
    public Team HomeTeam { get; set; }
    public int AwayTeamId { get; set; }
    public Team AwayTeam { get; set; }
}

public class Team
{
    ...
    public List<Game> HomeGames { get; set; }
    public List<Game> AwayGames { get; set; }
}

For a team it’s meaningful to make a distinction between home and away games, for example to compare results in both types of games.

And the mapping:

modelBuilder.Entity<Game>()
    .HasOne(g => g.HomeTeam)
    .WithMany(t => t.HomeGames)
    .HasForeignKey(t => t.HomeTeamId)
    .HasPrincipalKey(t => t.Id);
modelBuilder.Entity<Game>()
    .HasOne(g => g.AwayTeam)
    .WithMany(t => t.AwayGames)
    .HasForeignKey(t => t.AwayTeamId).OnDelete(DeleteBehavior.NoAction)
    .HasPrincipalKey(t => t.Id);

If using Sql Server, this delete behavior instruction is necessary to prevent disallowed multiple cascade paths.

More Related Contents:

  1. Entering keys manually with Entity Framework
  2. Many-to-many self referencing relationship
  3. navigation property should be virtual – not required in ef core?
  4. Can I reuse code for selecting a custom DTO object for a child property with EF Core?
  5. Filter all queries (trying to achieve soft delete)
  6. How to add the same column to all entities in EF Core?
  7. Dynamically changing schema in Entity Framework Core
  8. Include with FromSqlRaw and stored procedure in EF Core 3.1
  9. Could not load file or assembly Microsoft.Extensions.DependencyInjection.Abstractions, Version=1.1.0.0
  10. Entity framework EF.Functions.Like vs string.Contains
  11. The LINQ expression could not be translated and will be evaluated locally
  12. Entity Framework | Sequence contains more than one matching element
  13. Unable to edit db entries using EFCore, EntityState.Modified: “Database operation expected to affect 1 row(s) but actually affected 0 row(s).”
  14. Working with SQL views in Entity Framework Core
  15. Implementing recursive property loading in EF Core
  16. How to set Identity Seed value in code-first?
  17. Why does the EF 6 tutorial use asynchronous calls?
  18. One to one optional relationship using Entity Framework Fluent API
  19. How to compare only Date without Time in DateTime types in Linq to SQL with Entity Framework?
  20. Entity Framework – Cannot convert lambda expression to type ‘string’ because it is not a delegate type
  21. Internal .NET Framework Data Provider error 1025
  22. get date part only from datetime value using entity framework
  23. ASP.NET Identity – Multiple object sets per type are not supported
  24. Entity Framework Code Only error: the model backing the context has changed since the database was created
  25. Update records using LINQ
  26. Add migration with different assembly
  27. Seed Entities AND Users, Roles?
  28. Testing an Entity Framework database connection
  29. How should I access a computed column in Entity Framework Code First?
  30. MVC 4 – Many-to-Many relation and checkboxes

Leave a Comment