split code of 1,5,6 and 5,1-5.

Question

my problem is whenever user clicks the 1,5,6 link button it should be split and user clicks 5,1-5  button this is should be split please find the attachment. i wrote the code for 5,1-5.it is working but whenever user clicks the5,1-5. linkbutton it is showing error please help me.i bind the details into the pagesid.

public ActionResult GetPages(string PagesId)

        {

            if (!String.IsNullOrEmpty(PagesId))

            {

                string[] split = PagesId.Split(',');

                string[] split2 = split[1].Split('-');

                var sb = new System.Text.StringBuilder();

                for (int i = int.Parse(split2[0]); i <= int.Parse(split2[1]); i++)

                {

                    sb.Append(i.ToString());

                    sb.Append(",");

                }

                string output = split[0] + "," + sb.ToString().TrimEnd(',');