EF6 Configuring a Required-to-Optional Relationship (One-to–Zero-or-One

Question

I have two database tables called

SegmentSet SegmentSetGeometry

They both have primary key called SegmentSetId . (The SegmentSetGeometry (dependent) segmentSetId is foreign key to SegmentSet (primary)).

SegmentSets can have 0 or 1 SegmentSetGeometries

I have two classes representing these tables called SegmentSet and SegmentSetGeometry :

public class SegmentSet
{
    public long SegmentSetId { get; set; }
    // ...
    public virtual SegmentSetGeometry SegmentSetGeometry { get; set; }
}

public class SegmentSetGeometry
{
    public long SegmentSetId { get; set; }
    public DbGeometry Geometry { get; set; }

    public virtual SegmentSet SegmentSet { get; set; }
}

Here are their configurations:

public class SegmentSetConfiguration: EntityTypeConfiguration<SegmentSet>
{
    public SegmentSetConfiguration()
    {
        ToTable("SegmentSet");
        HasKey(x => x.SegmentSetId);

        // ...

        HasOptional(x => x.SegmentSetGeometry)
            .WithRequired(x => x.SegmentSet);
    }
}

public class SegmentSetGeometryConfiguration : EntityTypeConfiguration<SegmentSetGeometry>
{
    public SegmentSetGeometryConfiguration()
    {
        ToTable("SegmentSetGeometry");
        HasKey(x => x.SegmentSetId);
    }
}

When attempting to get a SegmentSet from the database the following error shows up:

Invalid column name 'SegmentSet_SegmentSetId'.

I found this reference https://docs.microsoft.com/en-us/ef/ef6/modeling/code-first/fluent/relationships and decided to switch the relationship and tried:

public class SegmentSetConfiguration: EntityTypeConfiguration<SegmentSet>
{
    public SegmentSetConfiguration()
    {
        ToTable("SegmentSet");
        HasKey(x => x.SegmentSetId);

        // ...
    }
}

public class SegmentSetGeometryConfiguration : EntityTypeConfiguration<SegmentSetGeometry>
{
    public SegmentSetGeometryConfiguration()
    {
        ToTable("SegmentSetGeometry");
        HasKey(x => x.SegmentSetId);
        HasRequired(x => x.SegmentSet)
            .WithOptional(x=>x.SegmentSetGeometry);

    }
}

But still doesn't work. I am using the example they give and it's not working, and I have looked at all the similar stack overflows and still not working

Answer 1

To map these two together, you should map from the required side of the relationship, and only that one side. Mapping both sides can lead to EF getting a bit garbled which may be causing your issue.

public class SegmentSet
{
    public long SegmentSetId { get; set; }
    // ...
    public virtual SegmentSetGeometry Geometry { get; set; }
}

public class SegmentSetGeometry
{
    public long SegmentSetId { get; set; }
    // ...
    public virtual SegmentSet SegmentSet { get; set; }
}

public class SegmentSetConfiguration: EntityTypeConfiguration<SegmentSet>
{
    public SegmentSetConfiguration()
    {
        ToTable("SegmentSets");
        HasKey(x => x.SegmentSetId);
        // Note: Do not map the HasOptional here... Only map the required on the other side.
    }
}

public class SegmentSetGeometryConfiguration : EntityTypeConfiguration<SegmentSetGeometry>
{
    public SegmentSetGeometryConfiguration()
    {
        ToTable("SegmentSetGeometries");
        HasKey(x => x.SegmentSetId);
        HasRequired(x => x.SegmentSet)
            .WithOptional(x=>x.Geometry);

    }
}

That should work as expected using the PK's on each table for the 1..0/1 relationship.

Edit: It's also worth checking that the Entity configurations are being loaded. That might explain EF falling back on convention. In the DbContext:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);
    modelBuilder.Configurations.AddFromAssembly(GetType().Assembly);
}

The above assumes the Entity Type Configs are in the same assembly as the DbContext definition. Otherwise: typeof(SegmentSetGeometryConfiguration).Assembly would do the trick.