Where clause using a lambda property selector

Question

I want to be able to refresh an object by finding it's match in list of objects that I've got back from the database. I can do it with reflection - but am sure there must be a way of getting the Property Selector within a Where clause.

This is the kind of thing I want to call ...

MyObject = GetRefreshedObject(MyObject, RefreshedObjects, () => ID);

But I'm a bit stuck with the Method!

    public static TE GetRefreshed<TE, P>(TE entity, IEnumerable<TE> refreshed, Expression<Func<TE, P>> selector) where TE : class
    {
        if (entity == null) return null;

        return refreshed.Where(x => x.[Selector == entity.Selector]).FirstOfDefault();

        //The square bracket bits obviously don't work but hopefully show what I'm trying to achieve!

    }

You have to apply the selector to the object, like selector(x) or somesuch. — bzlm
– bzlm, Commented Oct 12, 2011 at 15:25
Please don't prefix your questions with things like "c# Lambda". That's what the tags are for. — John Saunders
– John Saunders, Commented Oct 12, 2011 at 15:27

Jim Wooley · Accepted Answer · 2011-10-12 17:11:30Z

3

If you are just working with Lambdas and IEnumerables, do you really need the expression parsing? Use the lambda natively. That would require a slight change to your calling code:

var refreshedObject = GetRefreshedObject(MyObject, RefreshedObjects, x => x.ID);

The method implementation would be:

public static TE GetRefreshed<TE, P>(TE entity, IEnumerable<TE> refreshed, Func<TE, P> selector)
{
  P myObjectId = selector(entity);
  return refreshed.FirstOrDefault(refresh => selector(refresh).Equals(myObjectId));
}

answered Oct 12, 2011 at 17:11

Jim Wooley

10.4k1 gold badge27 silver badges44 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Where clause using a lambda property selector

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related