Same Table Many-To-Many Connection EF CodeFirst .net Core

Question

Hi i have a model class like

    public class Individual : EntityBase
{
    public Individual()
    {
        RelatedIndividuals = new HashSet<RelatedIndividual>();
    }

    public string FirstName { get; set; }

    public string PersonalNumber { get; set; }

    public ICollection<RelatedIndividual> RelatedIndividuals { get; set; }


}

This Individuals Will have some rrelated individuals With some relationType i want to have Many to many connections in same table so i created another class

    public class RelatedIndividual
{
    [Column("RelatedIndividualType")]
    public RelatedIndividualType RelatedIndividualType { get; set; }

    [Key, Column(Order = 0)]
    public long IndividualId { get; set; }

    [Key, Column(Order = 1)]
    public long RelatedIndividualId { get; set; }
}

and i tried to do in my contextDB

        protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Individual>()
            .HasMany(p => p.RelatedIndividuals)
            .WithMany()
            .Map(m =>
            {
                m.MapLeftKey("IndividualId");
                m.MapRightKey("RelatedIndividualId");
                m.ToTable("RelatedIndividual");
            });
    }

but i got error on WithMany

"Severity Code Description Project File Line Suppression State Error CS1061 'CollectionNavigationBuilder' does not contain a definition for 'WithMany' and no accessible extension method 'WithMany' accepting a first argument of type 'CollectionNavigationBuilder' could be found (are you missing a using directive or an assembly reference?) Repositories C:\Users\Luka\Desktop\Individuals\Repositories\Context\IndividualsDbContext.cs 23 Active "

any suggestions ? how to do it correctly ?

AFter Edit : I tried

    public class Individual : EntityBase
{
    public Individual()
    {
        RelatedIndividuals = new HashSet<RelatedIndividual>();
        RelatedIndividualsOf = new HashSet<RelatedIndividual>();
    }

    [MaxLength(50),MinLength(2), Column(TypeName = "nvarchar(50)")]
    public string FirstName { get; set; }
    [MaxLength(50), MinLength(2), Column(TypeName = "nvarchar(50)")]
    public string LastName { get; set; }

    public ICollection<RelatedIndividual> RelatedIndividuals { get; set; }
    public ICollection<RelatedIndividual> RelatedIndividualsOf { get; set; }
}

and my second class

    public class RelatedIndividual
{
    [Column("RelatedIndividualType")]
    public RelatedIndividualType RelatedIndividualType { get; set; }

    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public long IndividualId { get; set; }

    [ForeignKey("IndividualId")]
    public Individual Individual { get; set; }

    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public long RelateIndividualId { get; set; }

    [ForeignKey("RelateIndividualId")]
    public Individual RelateIndividual { get; set; }
}

and my context looks like this

        protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<RelatedIndividual>()
.HasKey(e => new { e.IndividualId, e.RelateIndividualId });

        modelBuilder.Entity<RelatedIndividual>()
                   .HasOne(pt => pt.Individual)
                   .WithMany(p => p.RelatedIndividuals)
                   .HasForeignKey(pt => pt.IndividualId);

        modelBuilder.Entity<RelatedIndividual>()
            .HasOne(pt => pt.RelateIndividual)
            .WithMany(t => t.RelatedIndividualsOf)
            .HasForeignKey(pt => pt.RelateIndividualId)
            .OnDelete(DeleteBehavior.Restrict);
    }

when i create physical person just it works ok , when i create physical person and in physical person i add RelatedIndividual , Ids doesnt match and it adds in both RelatedIndividuals and relatedIndividualsOf for example if my individual which i created newly is Id 2 and i related him to Id 1 when it saves in base its 2 , 2 not 1 ,2 help please.

Daniel Schmid · Accepted Answer · 2019-12-14 11:52:34Z

0

How would you store this information in a single database table?

But even if you could - EF core does not support many-to-many relationships directly. You need to define the join table so that you have two one-to-many relationships. This is how database modeling works.

EF 6 did create a join table implicitly but luckily EF core doesn't

answered Dec 14, 2019 at 11:52

Daniel Schmid

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1 Comment

lukacecxladze Over a year ago

yes i tried that as well i will edit it and check again.

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