public static void Main()
        {
            string[] str = { "abc", "bc", "cd", "ef" };
            var list = (from a in str
                       where a.Contains('c')
                       select a).ToList();
            var list2 = (from a in str
                         where a.Contains('b')
                         select a).ToList();
            List<string> ll = new List<string>();
            ll.AddRange(list);
            ll.AddRange(list2);
            foreach(var cc in ll)
                Console.WriteLine(cc);



        }

------解决方案--------------------

C# code
            string[] arr = { "abc", "bc", "cd", "ef","c1","a2","b2"};
            string[] str = { "a", "b", "c" };
            List<string> list = new List<string>();
            foreach (var c in str)
            {
                list.AddRange(arr.Where(n => n.Contains(c)).ToList());
                //or Concat
                //list = (list.Concat(arr.Where(n => n.Contains(c)))).ToList();
            }
            foreach (var o in list)
                Console.WriteLine(o);
            Console.ReadLine();