Question

I am using EF4.3 with a unit-of-work + repository pattern.

I have a method which act as a base of some other methods, here’s how the code looks.

This is my ‘base’ method:

    public static IQueryable<Deal> FindActive()
    {
        var r = new ReadRepo<Deal>(Local.Items.Uow.Context);

        return r.Find(d =>
            d.ActiveFrom <= DateTime.Now &&
            (d.ActiveUntilComputed == null || d.ActiveUntilComputed > DateTime.Now) &&
            d.Published);
    }

Here is one of the methods that calls the base method:

    public static IQueryable<Deal> FindActiveByStore(int storeId)
    {
        Guard.Default(storeId, "storeId");
        return FindActive().Where(d => d.StoreId == storeId);
    }

As you can see in FindActiveByStore, I first call FindActive, which then chains Find(). FindActive is followed by a Where() to add a secondary predicate (excuse the terminology).

I wondered if it was possible to pass a predicate to FindActive instead of using a Where(), and in fact whether it would make a difference in terms of performance.

Like this:

FindActive(d => d.StoreId == storeId)

FindActive already passes a predicate to Find() so it would need to combine both.

I’m guessing that the answers I get back will be along the lines ‘its not worth it’ in terms of effort or performance but I thought i’d ask the experts anyway.

Answer 1

You can use this code (You reduce number lines of code)

public IQueryable<Deal> FindActiveByStore(Expression<Func<Deal,bool>> predicate)
{
  var r = new ReadRepo<Deal>(Local.Items.Uow.Context);

  return r.Find(d => d.ActiveFrom <= DateTime.Now 
             && (d.ActiveUntilComputed == null || d.ActiveUntilComputed > DateTime.Now) 
             && d.Published)

             .Where(predicate);   
}