Sol 1. public static bool In(this T item, params T[] items) { if (items == null) throw new ArgumentNullException("items"); return items.Contains(item); } 1. 예) int ix= 1; if (ix.In(1, 2, 3)) string s1= "B"; if (s1.In("A", "B", "C")) Sol 2. public static bool In(object compare, params string[] sList) { for (int index = 0; index < sList.Length; ++index) { if (sList[index] == compare.ToString()) re..