Multiplicity conflict while setting up Entity Framework

Question

I have a more complicated question here

But thought I would simplify it.

Here are my dummied classes (the structure this is based on comes from the NDC so I don't have control over it):

public class RightHand
{
    [Key]
    public int RightHandId { get; set; }
    public string PropertyA { get; set; }

    [Required]
    public virtual Linker Linker { get; set; }
}

public class LeftHand
{
    [Key]
    public int LeftHandId { get; set; }
    public string PropertyB { get; set; }

    [Required]
    public virtual Linker Linker { get; set; }
}

public class Linker
{
    [Key]
    public int LinkerId { get; set; }
    [ForeignKey("RightHand")]
    public int RightHandId { get; set; }
    [ForeignKey("LeftHand")]
    public int LeftHandId { get; set; }
    public string PropertyC { get; set; }

    [Required]
    public virtual RightHand RightHand  { get; set; }
    [Required]
    public virtual LeftHand LeftHand  { get; set; }
}

I've tried so many things so hopefully this simplified version can help someone help me.

Over all, I want to search on:

LeftHand.PropertyB and see the properties for RightHand
As well, I want to search on RightHand.PropertyA and see the properties for Left Hand

All in all, I don't care about Linker except that is what links LeftHand to RightHand. LeftHand and RightHand are one-to-one.

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<RightHand>()
            .Property(x => x.RightHandId)
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);

        modelBuilder.Entity<LeftHand>()
            .Property(x => x.LeftHandId)
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);

        modelBuilder.Entity<Linker>()
            .Property(x => x.LinkerId)
            .HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);

        modelBuilder.Entity<Linker>()
            .HasRequired(nus => nus.LeftHand)
            ;

        modelBuilder.Entity<Linker>()
            .HasRequired(nuu => nuu.RightHand)
            ;
    }

Thanks, I am using VS2017, EF 6.2, Code First, SQL Server

I have tried different annotations but the one common error is:

Linker_LeftHand_Source: : Multiplicity is not valid in Role 'Linker_LeftHand_Source' in relationship 'Linker_LeftHand'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be '*'.

Linker_RightHand_Source: : Multiplicity is not valid in Role 'Linker_RightHand_Source' in relationship 'Linker_RightHand'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be '*'.

What is different here than other multiplicity answers is the middle linker table.

Possible duplicate of [Entity Framework 4.0: Error 113: Multiplicity is not valid in Role](https://stackoverflow.com/questions/9292738/entity-framework-4-0-error-113-multiplicity-is-not-valid-in-role) — vivek, Apr 10 '19 at 16:59
@vivek just because I get the same error message does not necessarily mean same cause. — Gina Marano, Apr 10 '19 at 17:05
@GinaMarano See my answer please! I have explained it and given the solution. — TanvirArjel, Apr 10 '19 at 17:19

score 1 · Accepted Answer · answered Apr 10 '19 at 17:13

1

As Entity Framework 6.x does not support one-to-one relationship with explicit Foreign Key property and if you try to workaround it with ForeignKey data annotation, you'll get multiplicity error during the migration.

So only solution is: Remove RightHandId and LeftHandId properties from Linker model class as follows:

public class Linker
{
    [Key]
    public int LinkerId { get; set; }
    public string PropertyC { get; set; }

    public RightHand RightHand { get; set; }
    public LeftHand LeftHand { get; set; }
}

Then your model configurations should be as follows:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<LeftHand>().HasOptional(l => l.Linker)
            .WithOptionalPrincipal(lf => lf.LeftHand)
            .Map(lf => lf.MapKey("LeftHandId"));

        modelBuilder.Entity<RightHand>().HasOptional(l => l.Linker)
            .WithOptionalPrincipal(lf => lf.RightHand)
            .Map(lf => lf.MapKey("RightHandId"));
 }

answered Apr 10 '19 at 17:13

TanvirArjel

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I will give this a try... Only confused on how to seed the database – Gina Marano Apr 10 '19 at 19:06
Mapping Navigation properties! – TanvirArjel Apr 10 '19 at 19:07
Wow! this is the closest I have gotten. Database structure is correct. Left and right (well, the actual table names) have been populated. CsvHelper is probably puking on Linker.RightHand and Linker.LeftHand when seeding. – Gina Marano Apr 10 '19 at 19:36
1

You have to use `.Include(x => x.Linker)` – TanvirArjel Apr 11 '19 at 06:17
thanks. But I found out the cause. The import didn't keep my primary key values, it reset them so nothing matches up. I'm looking into it... – Gina Marano Apr 11 '19 at 06:24
(fixed my import issue), using include, I have Linker now. How do I get LeftHand from Linker? – Gina Marano Apr 11 '19 at 06:30

Multiplicity conflict while setting up Entity Framework

1 Answers1