Работа с файлами

class OpenSaveSetting
    {
        public static void Open(ref Setting set) 
        {
            XmlSerializer xml = new XmlSerializer(typeof(Setting));
            using (StreamReader stream = new StreamReader("serversetting.xml"))
            {
                set = (Setting)xml.Deserialize(stream);
                stream.Close();
            }
        }
 
        public static void Save(Setting set) 
        {
            XmlSerializer xml = new XmlSerializer(typeof(Setting));
            using (StreamWriter stream = new StreamWriter("serversetting.xml"))
            {
                xml.Serialize(stream, set);
                stream.Close();
            }
        }
    }
 
    public class Setting 
    {
        string serverhostname;
        string port;
        string namedatabase;
 
        public string ServerHostName 
        {
            get { return serverhostname; }
            set { serverhostname = value; }
        }
 
        public string Port 
        {
            get { return port; }
            set { port = value; }
        }
 
        public string NameDataBase 
        {
            get { return namedatabase; }
            set { namedatabase = value;}
        }
    }

using System.IO;
using System.Xml.Serialization;

private void button1_Click(object sender, EventArgs e)
        {
             //поиск
            string connstr = System.Configuration.ConfigurationSettings.AppSettings["CheckingPath"];
            /*SqlConnection sqlConnection1 = new SqlConnection("Data Source=microsof-6b2e38\\sqlexpress1;Initial Catalog=Diploma;Integrated Security=True ");*/
            SqlConnection sqlConnection1 = new SqlConnection(connstr);
            SqlCommand cmd = new SqlCommand();
            SqlDataReader reader;
            string param = comboBox1.Text;
            cmd.CommandText = "select * from Mainwindow1 where (Equipment_Name like '%" + comboBox1.Text + "%') and (Phone_Number like '%" + comboBox2.Text + "%') and (Job_Name like '%" + comboBox3.Text + "%')and (Tseh_Num like '%" + comboBox5.Text + "%')and (FIO like '%" + textBox1.Text + "%')and (Tseh_Num like '%" + comboBox4.Text + "%') and (Station_Name like '%" + comboBox7.Text + "%') ";
            cmd.Connection = sqlConnection1;
            sqlConnection1.Open();
            reader = cmd.ExecuteReader();
            DataTable dt1 = new DataTable();
            dt1.Load(reader);
            dataGridView2.DataSource = dt1;
            sqlConnection1.Close();

SqlConnection sqlConnection1 = new SqlConnection(Properties.Settings.Default.MyConnectionString);