C#読み出しxml

xml  ：
<?xml version="1.0" encoding="utf-8" ?>
<config>
  <mxd>
    <map>c:\\aa.mxd</map>
    <over>c:\\bb.mxd</over>
  </mxd>
  <scale>
    <num>4</num>
    <num>3</num>
    <num>2</num>
    <num>1</num>
  </scale>
</config>


  ：
string map;
        string over;
        int[] nums =new int[4];
        public bool test()
        {
            //DataTable dt = new DataTable();
            try
            {
                DataSet sd = new DataSet();
                string str = System.Environment.CurrentDirectory + @"\config.xml";
                sd.ReadXml(str);
                map = sd.Tables["mxd"].Rows[0]["map"].ToString();
                over = sd.Tables["mxd"].Rows[0]["over"].ToString();
                for (int i = 0; i < sd.Tables["num"].Rows.Count; i++)
                {
                    string temp = sd.Tables["num"].Rows[i][0].ToString();
                    nums[i] = int.Parse(temp);
                }
            }
            catch {
                return false;
            }
            return true;
        } 

using System;
using System.Xml;
using System.IO;
using System.Data;

if (sd.Tables["num"] != null)