Question

When using Linq-To-SQL or Entity Framework, the DataContext and generated entities provide IQueryable interfaces for deferred execution. It lets me write code like this:

public class RPO
{
    DataContext dc;
    public RPO(){ dc = new DataContext(); }
    public IQueryable<Data> ReadData()
    {
        return dc.Data;
    }
}

public class Svc
{
    RPO repository;
    public Svc() { repository = new RPO(): }
    public IQueryable<Data> ReadActiveData() 
    { 
        return repository.ReadData().Where(d => d.IsActive.Equals(true)); 
    }
    public IQueryable<Data> ReadArchiveData() 
    { 
        return repository.ReadData().Where(d => d.IsArchived.Equals(true)); 
    }
}

This model falls appart if in the class Svc I return DataModel instead of Data — how can I keep IQueryable<T> as far down the chain as possible?

Answer 1

Your SVC layer should never expose IQueryable. What happens then is, it is actually your service consumer who gets to execute your query which is a bad pattern. So service should always expose
data which is sufficient for the service-user to work ( display) with.

Preferably a IList or a IEnumarable.