A Complete Class Code with Difference Method In cluding Email Send,

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using System.Net.Mail;
/// <summary>
/// Summary description for Class1
/// </summary>

namespace DBhandler
{
    public class DBhandler
    {
        SqlConnection con = new SqlConnection();
        SqlCommand cmd = new SqlCommand();
        SqlDataAdapter da = new SqlDataAdapter();
        SqlDataReader dr;
        DataSet ds = new DataSet();

        public DBhandler()
        {
            con.ConnectionString = ConfigurationManager.ConnectionStrings["Con"].ConnectionString;
            if (con.State == ConnectionState.Closed)
            {
                con.Open();
            }
        }
        public void update(string Query)
        {
            cmd.CommandText = Query;
            cmd.Connection = con;
            cmd.ExecuteReader();
        }
        public int select(string str, string username, string password)
        {
            int f = 0;
            cmd.CommandText = str;
            cmd.Connection = con;
            cmd.CommandType = CommandType.StoredProcedure;
            dr = cmd.ExecuteReader();
            while (dr.Read())
            {

                if (username.Trim().ToString() == dr.GetString(0).Trim().ToString() && password.Trim().ToString() == dr.GetString(1).Trim().ToString())
                {
                    f = 1;
                    return f;
                }

            }
            return f;
        }
    

        public int check(string chk, string username)
        {


            int f = 0;
            cmd.CommandText = chk;
            cmd.Connection = con;
            dr = cmd.ExecuteReader();
            while (dr.Read())
            {
                if (username.Trim().ToString() == dr.GetString(0).Trim().ToString())
                {
                    f = 1;
                    return f;
                }
               

            }
            return f;
        }


        //public string selected(string chk, string uname)
        //{
        //    string str;
        //    cmd.CommandText = chk;
        //    cmd.Connection = con;
        //    dr = cmd.ExecuteReader();
        //    while (dr.Read())
        //    {
        //        if (dr.GetString(0) == uname)
        //        {
        //            str = dr.GetString(1);
        //            return str;
        //        }
        //    }
        //}

        /*  show one record in detail view*/

        public DataSet getdata(string str)
        {
            ds.Clear();
            cmd.CommandText = str;
            cmd.Connection = con;
            da.SelectCommand = cmd;
            da.Fill(ds);
            return ds;
            ds.Clear();
        }

        public void SendMail(string From, string Email, string Subject, string Body)
        {
            SmtpClient Smtp = new SmtpClient("WebMail.nanipublicschool.com");
            MailMessage message = new MailMessage(From, Email);
            message.IsBodyHtml = true;
            message.Subject = Subject;
            message.Body = Body;
            Smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
            Smtp.Host = "127.0.0.1";
            Smtp.Port = 25;
            Smtp.UseDefaultCredentials = true;
            Smtp.Send(message);
        }

        public void getfield(string str)
        {

            string data;
            cmd.CommandText = str;
            cmd.Connection = con;
            dr = cmd.ExecuteReader();
            while (dr.Read())
            {
                data = dr.GetString(0).Trim().ToString();
            }

        }

    }

}