Entity Framework Code First foreign key

Question

I have problem with creating relation. What is the best desing in scenerio similar to this. I have one common class "Image" to all other classes which contain images. One image should have only one class. But sometimes it is Class1, other time Class2 etc.

public class Class1
        {
            int Id ;
            List<Image> Images;
        }
        public class Class2
        {
            int Id;
            List<Image> Images;
        }
        public class Class3
        {
            int Id;
            List<Image> Images;
        }
        public class Image
        {
            int Id;
            int IdClass1;
            int IdClass2;
            int IdClass3;

            public Class1 Class1;
            public Class2 Class2;
            public Class3 Class3;
        }

Are those navigation properties? If so, shouldn't they be `virtual` and the lists be `ICollection `? — Mathieu Guindon, Aug 08 '13 at 19:42
Yes those are navigation proporties and you are right. But mayby I should implement it in different way. — Malv20, Aug 08 '13 at 20:05
This is called _polymorphic associations_. See [here](http://stackoverflow.com/q/8895806/861716) for more details. — Gert Arnold, Aug 08 '13 at 22:54

score 0 · Answer 1 · answered Aug 08 '13 at 19:37

0

I would suggest making the Class1, Class2, Class3, and corresponding identifiers nullable. You would have to enforce constraints at the code level though, instead of relying on the database for those constraints.

answered Aug 08 '13 at 19:37

Joe Brunscheon

1,949
20
21

Yes I can but what if I had 10 more classes it could be overwhalming. I think that it isn't the best approach. I was thinking about giving to all classes GUID identifier and than my image could have only ID, directory and GUID referencing to corresponding object. But I'm not sure. – Malv20 Aug 08 '13 at 20:09
Then you should change your design. Try defining a junction table (class really) of some kind that would link a "class" to a bunch of images. Then each class would have a list of these junctions as part of its model. – Joe Brunscheon Aug 08 '13 at 20:17

Entity Framework Code First foreign key

1 Answers1