请问像下面这样怎么做
例如：A="15,2,7,8,9,6,2"
B="15,6,7,81,91,62,23"
要把他合并一起成：
C="15-15,2-6,7-7,8-81,9-91,6-62,2-23"  青椒怎么弄

      string a = "1,2,3,4";
            string b = "5,6,7,8";
            string[] arra = a.Split(',');
            string[] arrb = b.Split(',');
            string c = "";
            for (int i = 0; i < arra.Length; i++)
            {
                c += arra[i] + "-" + arrb[i] + ",";
            }
            Console.WriteLine(c.TrimEnd(','));