in this code am getting error any one solve this

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Xml;
using System.Data;
public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            XmlDocument doc = new XmlDocument();
            doc.Load(Server.MapPath("C:\\Documents and Settings\\anush\\Desktop"));
            XmlNodeList bookList = doc.GetElementsByTagName("DocumentElement");
            foreach (XmlNode node in bookList)
            {
                XmlElement bookElement = (XmlElement)node;
                string ctry = bookElement.GetElementsByTagName("DocumentElement")[0].InnerText;
                ddl.Items.Add(ctry);
            }
        }
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        DataTable dt = new DataTable();
        DataColumn dc = new DataColumn("id");
        DataColumn dc1 = new DataColumn("DataBaseName");
        dt.Columns.Add(dc);
        dt.Columns.Add(dc1);
        string ct = ddl.SelectedItem.ToString();
        string dataPath = Server.MapPath("C:\\Documents and Settings\\azhar\\Desktop\\appsettings.xml");
        DataSet dSet = new DataSet();
        dSet.ReadXml(dataPath);
        DataRow[] rows = dSet.Tables[0].Select(" DataBaseName= '" + ct + "'");
        foreach (DataRow dr in rows)
        {
            DataRow myRow = dt.NewRow();
            myRow["id"] = dr["id"];
            myRow["DataBaseName"] = dr["DataBaseName"];
            dt.Rows.Add(myRow);
        }
        grxml.DataSource = dt;
        grxml.DataBind(); 
    }
}