Foreign Key Questions

Our database has a lot FKs that are integers. Some of them are required filed, some of them are not.  I have some questions:

 

1.      For required FK,  how do you write your own verifier? DevForce’s default verifier for required FK is always returns OK, no matter what. I tried to write a range verifier for the required FK, it always returns OK too.   How do you enforce the required FK?

2.      In edit screen, how do you fill the ComboBox of non-required FK? Add a null entity? Since it is not required, the user should be able to change the ComboBox to select nothing.

 

Any help/suggestion would be appreciated.

 

 

Thanks!

 

Amy

#1   I mentioned in my question: I did add a range verifier, but it returns OK. Is anything wrong with following code?

{ return new Int32RangeVerifier(typeof(Vehicle), Vehicle.Operation_fk_OperationIDEntityProperty.Name,

true, 0, int.MaxValue);}

#2 We also added an NullEntity on each non-requied FK. Since we have  a lot FKs,  wish there is a better solution.

 

 

Thanks!

I haven't done this for EF yet, but in DevForce classic, I took a different approach that worked really well for discovering potential FK violations prior to saving to the database.

1) I created an algorithm that looks at all EntityRelations and discovers all relations where the parent entity is required.  This process discovers the parent property descriptor for the parent relation and looks for the "RequiredValueVerifierAttribute" on that property.  It's a bit complex, but it works great for discovering the parent required properties.

2) I created a "NotNullEntityVerifier" that fails if an entity is the null entity.

3) I created a helper method that, when given an entity type, adds a NotNullEntityVerifier to the VerifierEngine for all required parent properties of the given type.

When all is said and done, all I have to do is go to my GetVerifiers static method for an entity type and do this:

        [VerifierProvider]
        public static IEnumerable<Verifier> GetVerifiers(Object pVerifierProviderContext)
        {
            var engine = GetEngineFromVerifierProviderContext(pVerifierProviderContext);
            var list = new List<Verifier>();
            list.AddParentRequiredVerifiers<Employee>();
            return list;
        }

If you are so inclined, you could even call this method for all entity types in your Model assembly all at once rather than calling this once for each entity type (though in a large model this may not be advisable).

It's almost like magic when your Foreign Keys are enforced completely in the middle tier.

If any one is interested in the code, post on this thread and I'll try to find time to clean up and add this code to the DevForceContrib project on CodePlex (http://devforcecontrib.codeplex.com/).


--Jeff

Check if FK > 0 is not really working. When adding parent, also adding related children in the same time, the FKs for children  are negative.