dotnetfunda.com/articles/article71.aspx

UI:Login Page

 public partial class login : System.Web.UI.Page
{
businessLogic obj = new businessLogic();
protected void button_Click(object sender, EventArgs e)
{
obj.Username = username.Text;obj.Password = password.Text;
obj.loginbll();
Response.Redirect("HOme.aspx");
}
}

BLL:using databaselogic;

public class businessLogic {public businessLogic ()
{
databaselogic obj_Bl = new databaselogic();
}
public string _username, _password;
public string Username
{
get
 { 
return _username;
 }
set 
{ 
_username= value; 
}
}
public string Password
{
get
 {
 return _password;
 }
set
 { 
_password = value;
 }
}
public void loginbll()
{
obj_Bl.login(Username,Password);
}

DAL:namespace databaselogic

{

public class databaselogic
{
public databaselogic()
{
}
public void login(string username, string password)
{
//code related to Queries goes on here
}
}
}