Can I do model-level filtering in Entity Framework?

Question

In the latest version of Lightswitch, they have added a query pipleline method that allows you to catch all query requests to the database, and add a filter. This allows you

Answer 1

You have to be able to intercept and modify your predicates.

One. If you've abstracted your repository then you could do something like this:

All your Entities could inherit from an Abstract class or Interface with and Active property and your code would be:

    interface IActivatable {
        bool IsActive {get;set;}
    }


    class Repository<EntityType>
        where EntityType : class, IActivatable {

        private StackOverflowEntities context;


        public IQueryable<EntityType> GetAll() {

                return context.Set<EntityType>().Where(e => e.IsActive == false);

        }
    }

That way the GetAll returns the IQueryable with an initial predicate, the rest will be added with an AND. Like so:

            Repository<Person> persons;
            var results = persons.GetAll().Where(p => p.IsMarried == false);

Which will result in a predicate equal to p.IsMarried == false && p.IsActive == false

Two. If it's not practical to change your repository code or code at all you could create a view for every table. The view can just include the IsActive in the where clause to exclude the records and then reload your EDMX based on those views - at least this is the way we used to do in back in the day.

Edit:

Three. If you have a generated DbContext exposed to client code you could do this:

    public partial class StackOverflowEntities : DbContext
    {
        public StackOverflowEntities()
            : base("name=StackOverflowEntities")
        {
        }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();            
        }

        public DbSet<Blog> Blogs {
            return this.Set<Blog>().Where(b => b.IsActive == false);
        }
    }

Just means that you must turn off auto-code gen or modify the T4 template. Easier to just take the generated code, turn of the gen and modify.