I want to split string array on basis of _ in the string

<pre> public DataSet AutogenerateServiceno()
        {
            con.Open();
            SqlCommand cmd = new SqlCommand("Proc_autogeneratesvno1", con);
            cmd.CommandType = CommandType.StoredProcedure;
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            DataSet ds = new DataSet();
            da.Fill(ds);
            return ds;
           
        }

sv_10
sv_11
sv_12
sv_4
sv_9

 public string AutogenerateSvno()
        {
            string s2 = "sv_";
            DataSet ds = objdal.AutogenerateServiceno(); //  here values in s=sv_10, sv_11, sv_12, sv_4, sv_9.
// now I want seperate Sv and number seperate and want to insert number in one // //arrar and number values in another array i.e values 10,11,12,4,9 in one array.
// then I want to find Highest Number from numeric array and in that number //increment by one and then concate that incremented number to sv_(number) and //return that values to presentation layer  for that I have written following code.
//but it giving exception at  
                arrval1[i] =Convert.ToString(arrvalues[i].Split('_'));
           
 string[] arrvalues = new string[ds.Tables[0].Rows.Count];
            string[] arrval1 = new string[ds.Tables[0].Rows.Count];
            int[] arrval = new int[ds.Tables[0].Rows.Count];

            //loopcounter
            for (int loopcounter = 0; loopcounter < ds.Tables[0].Rows.Count; loopcounter++)
            {
                string str;
               // .Split('_');
                //assign dataset values to array
                arrvalues[loopcounter] =ds.Tables[0].Rows[loopcounter]["svno"].ToString();
            }
            for (int i = 0; i < arrval.Length - 1; i++)
            {
                arrval1[i] =Convert.ToString(arrvalues[i].Split('_'));  // Error Here
                arrval[i] = int.Parse(arrval1[i]);
            }
            //string[] s1 = s.Split('_');
            //int i = int.Parse(s1[1]);
            //i++;
            //s2 = s2 + i
            return s2;
        }