How to tell if a property of an EntityObject is a primary key or foreign key? - sql

Question

Suppose that I have a class generated by Entity Framework called Student.
Student has the following properties:
Id int,
Name, string
Age, int
TeacherId int
Suppose further that Id refers to the primary key in SQL that identifies what student a Student object refers to and TeacherId is a foreign key that tells who the student's teacher is.
Suppose I want to write a function which takes any EntityObject (such as this one) as a parameter and returns information about which properties are primary keys and foreign keys.
How can I do this?
If this is not appropriate, then how can Entity Framework tell me which properties are primary and foreign keys?
For now, let's not take into consideration composite key fields.

Answer 1

Looking over the code that is autogenerated, I can see that primitive properties in the generated class have several attributes, and among these is an EdmScalarPropertyAttribute which has a boolean EntityKeyProperty which seems to indicate whether or not the property is a key.
How to read the values of the attributes is described in an article here: http://msdn.microsoft.com/en-us/library/71s1zwct.aspx
I'll bet that I can find a consistent pattern for how foreign keys are handled as well!

Answer 2

I have little support section in Repository for such questions.
See the GetEntityKeyFields method below
I dont have check routine already written FK, but if you check the entityField details, it will be there as well.
public DbEntityEntry<T> Entry(T entity) { return Context.Entry(entity); }
public DbSet<T> EntityDbSet() { return Context.Set<T>(); } // cant be in core interface since it is EF types
public ObjectContext ObjectContext { get { return ((IObjectContextAdapter) this.Context).ObjectContext; } }
// cant be in core interface since it is EF types
public BosBaseDbContext Context { get; protected set; }
public EntityState GetEntityState(T entity) { return Context.Entry(entity).State; }
public ObjectSet<T> GetObjectSet() { return ObjectContext.CreateObjectSet<T>(); }
public string[] GetEntityFields() { return GetObjectSet().EntitySet.ElementType.Properties.Select(e => e.Name).ToArray(); }
public string[] GetEntityKeyFields() { return GetObjectSet().EntitySet.ElementType.KeyMembers.Select(k => k.Name).ToArray(); }
public EntityKey GetEntityKey(T entity) {
if (entity == null) {
return null;
}
return ObjectContext.CreateEntityKey(GetObjectSet().EntitySet.Name, entity);
}