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I'm having a problem with a mapping in Entity Framework.

I have the following classes (simplified):

public class Building
{

    public int ID { get; set; }     
    // *.. snip..* other properties
    public Location Location { get; private set; }
}

public class Location
{
    public string Street {get; set;}
    public Country country {get; set}
}
public class Country
{
    public int ID { get; set; } 
    public string Name { get; set; } 
}

Building and Country are entities, they are saved in the database. Location is a value type and should map to the same table as Building.

However, when I map it this way, entity framework wants to map Location to a table as well and is complaining it has no Key. I don't want to give it a key since it belongs to the Building and should not be an entity at all.

I have seen workarounds which say you need to put Country on the Building-class, but that just doesn't feel good (and is semantically just plain wrong).

I'm using Entity Framework 5

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You're looking for complex types. – Gert Arnold Jun 24 '13 at 12:14
1  
Yes, I know, the problem is that as soon as that complex type has a reference to an entity, EF wants to put the complex type in a table as well – Kenneth Jun 24 '13 at 13:01
    
What a nice question. Actually, I usually put focus on domain logic, and I don't care at all about how the ORM persists data (therefore I wouldn't see adding an Id column in Location as a big problem). If I really had to care about how data is stored, I'd consider not mixing domain objects with ORM entities, by creating a specific layer to persist (creating entities to attend ORM), though this might put more complexity in the archicteture. If you came to a conclusion, let us know, maybe CQRS solves this. – Alisson Jun 11 '16 at 4:51
    
Yeah, in the end, I just got rid of EF. No ORM is much simpler :-) – Kenneth Jun 13 '16 at 14:30
    
You could use NHibernate instead of the EF. Here you can do that things. – Brian J. Hakim Aug 7 '16 at 16:27
up vote -3 down vote

You may mark Location property in Building class with [NotMapped] Attribute. 

using System.ComponentModel.DataAnnotations.Schema;
public class Building
{
    [NotMapped]
    public Location Location { get; private set; }
}

Hope that solves your problem!

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I don't think this is what he's looking for. This wouldn't save the locations of entities which is what he wants to do. – Jeroen Vannevel Jun 24 '13 at 12:43
    
Indeed, that doesn't solve it. I want Location inside the Building-table with a reference to the countries-table. I need it mapped – Kenneth Jun 24 '13 at 13:01
    
In that case, I think you will have to map 'location' to a table which relates Building and country tables. – Devasayal Jun 24 '13 at 13:39
    
Hm, I wanted to avoid that. My database structure shouldn't be dependend on my domain model. The location data just belongs to the Building, it shouldn't be in a separate table. – Kenneth Jun 24 '13 at 13:43

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