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Editorial Team
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Asked: 2026-06-15T15:51:31+00:00

I am doing code first and using a Table-per-type design. I am getting the

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I am doing code first and using a Table-per-type design. I am getting the following error when I extend the second object to multiple tables:

A value shared across entities or associations is generated in more than one location. Check that mapping does not split an EntityKey to multiple store-generated columns.

My database looks like:

Thanks for the up-vote, editing to add my picture:
enter image description here

The POCO for the project looks like:

public abstract class Project {
    public int ProjectID { get; set; }
    public string Title { get; set; }
    public string Description { get; set; }
    public virtual ICollection<Tag> Tags { get; set; }
    public virtual ICollection<LocationElement> LocationElements { get; set; }


    public abstract string getProjectIdentifier();

}

And for a Location Element:

public enum HowObtainedCodes {
    Provided = 1,
    Estimated = 2,
    Summarized = 3
}
public abstract class LocationElement {
    public int LocationElementID { get; set; }
    public int ProjectID { get; set; }
    public HowObtainedCodes HowObtainedCodeID { get; set; }
}

And for a point:

[Table("ProvidedPoints")]
public class ProvidedPoint : LocationElement {
    public double Lat { get; set; }
    public double Long { get; set; }
    public string Description { get; set; }
}

The link from projects (abstract) to scientific licences works fine, and my objects load / persist as expected. Further I can add LocationElements object in if I make it not abstract. As soon as I extend LocationElements and try to save a ProvidedPoint object I get the above message. My first thought was that the LocationElementID on ProvidedPoints was set as an Identity column, but this was not the case.

My question is: Am I doing something unexpected by trying to link two TPT objects together in this way? Am I missing something else?

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1 Answer

  1. Editorial Team

    As noted by @leppie above, I had to decorate the LocationElement class with the annotation [Table(“LocationElements”)], which immediately fixed the problem. My understanding with EF was that this was not necessary with the base table for a TPT design, and further I had not done it on the Project / ScientificLicence pair (that is, I only decorated the ScientificLicence object).

    I am assuming this has something to do with the way LocationElements are added/persisted when I save a new Project object. If anyone has any additional insight I would love to know more.

    Hope this helps someone else and a big thank you to leppie!

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