Adrian Alonso

The .Net fx doesn't have any support to compose Predicates so I decided to create a Predicates helper for a small project I was working on the last weeks. Here you have my composite predicate methods:

    public static class Predicates
    {
        public static Predicate<T> And<T>(Predicate<T> predicate, Predicate<T> anotherPredicate)
        {
            return delegate(T t) { return predicate(t) && anotherPredicate(t); };
        }

        public static Predicate<T> Or<T>(Predicate<T> predicate, Predicate<T> anotherPredicate)
        {
            return delegate(T t) { return predicate(t) || anotherPredicate(t); };
        }

        public static bool Is<T>(object target, Predicate<T> predicate) where T : class
        {
            T targetAsT = target as T;
            if ( null != targetAsT  )
            {
                return predicate(targetAsT);
            }
            return false;
        }

        public static Predicate<T> GetNullPredicate<T>()
        {
                return delegate(T t) { return true; }; 
        }
    }

The Is<T> method allows you to validate if the target object is of T type before evaluating the predicate. This is something I found very useful when I am working with VS Automation Model because there are "Objects" that can implement many many interfaces so you have a collection of those objects that may or not target the T type. I will publish another post with a Finder example.

Labels: .Net

# posted by Adrian Alonso : 3:20 PM