How to I add a new value based on a change of value

Hi there

How to I add a new value based on a change of value?

I have this code

 foreach (var item in itemAttributes)
        {            
            string fID = GetBook("Programming");
            var attributes = from a in itemAttributes
                             where a.Description.ToLower().Contains("ID='" + fID + "'")

            SearchBookCollection values = new SearchBookCollection();
            values.AddRange(attributes.ToList());
        }

What I want is if fID are different ONLY run

values.AddRange(attributes.ToList());

Hope this makes sense?

thanks