public static GrowSize Instance(int rate, int target)
 {
     var key = new Tuple<int, int>(rate, target);
     GrowSize ret;
     if (!instances.TryGetValue(key, out ret))
         ret = instances[key] = new GrowSize(rate, target);
     return ret;
 }
        public static GrowSize Instance(int rate, int target)
        {
            var      key = new Tuple <int, int>(rate, target);
            GrowSize ret;

            if (!instances.TryGetValue(key, out ret))
            {
                ret = instances[key] = new GrowSize(rate, target);
            }
            return(ret);
        }