gistfile1.cs

    class Test<PageType> : DbContext
        where PageType : class
    {
        private Dictionary<Type, PageType> callbacks = new Dictionary<Type, PageType>();

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);

            foreach (var type in callbacks.Keys)
            {
                var entity = modelBuilder.Entity<Page>();
                var callback = this.GetType().GetMethod("InternalMap").MakeGenericMethod(type);

                entity.GetType().InvokeMember("Map", BindingFlags.InvokeMethod, null, entity, new object[] { type });
            }
        }

        private void InternalMap<TEntityType>(EntityMappingConfiguration<TEntityType> m)
        {
            m.Requires("PageTypeId").HasValue(callbacks[typeof(TEntityType)].PageTypeId);
            m.MapInheritedProperties();
        }
    }