using System;
 
public delegate bool Predicate<T, U> (T arg1, U arg2);
 
public static class EventHelper
{
    public static EventHandler<T> Filter<T> (Predicate<object, T> predicate,
        EventHandler<T> handler) where T: EventArgs
    {
        EventHandler<T> filtered = (object sender, T args) => {
            if (predicate (sender, args)) {
                handler (sender, args);
            }
        };
 
        return filtered;
    }
}