How to write the business logic codes for an application ?...

hai Karthi
i given some example to handle Business logic and DataLayer.

Create two class files,like BL.cs and ProductProperties.cs

*to write all Business related functionality in BL.cs


to write code for Login verification (Login Button Click event)

protected void Login_click(object sender, EventArgs e)

{
    // to set properties
     ProductProperties Obj=new ProductProperties();
    Obj.UserName=TextBox1.text;
    Obj.Password=TextBox2.text;
    //to create Object for BL.cs
    BL ObjBL=new BL()
     if(ObjBL.isvalid())
    {
        //login sucessfully...   
    }
    else
    {   
        invalid username or password...   
    }
}

----------------------------------------------------------------

public class ProductProperties
{
   
  private string userName,Password;
  public string UserName
  {
    set{userName=value;}
    get{return userName;}
  }
  public string Password
  {
    set{password=value;}
    get{return password;}
  }
// to write like this for all needed variables..
}

----------------------------------------------------------------
public class BL
{
    public BL()
    {
    //to establish the connection...
    }
   
    //to call DB using DataSet or ExecuteScalar
    public boolen isvalid(ProductProperties Obj)
    {
   
    //to validate username and password using Querystring or StoredProcedure if  valid hten return true else return false here am using storedProcedure.
    SqlCommand cmd = new SqlCommand();
    cmd.Parameters.Add("@loginID", SqlDbType.VarChar).Value = TextBox1.Text;//loginID-procedure first argument
    cmd.Parameters.Add("@Password", SqlDbType.VarChar).Value = TextBox2.Text;//Password-procedure second argument
    cmd = new SqlCommand("submitrecord", con);//submitrecord-stored procedure name
    cmd.CommandType = CommandType.StoredProcedure;
    con.Open();
    isValidUser=(cmd.ExecuteScalar().Hasrow)
    con.Close()
   
            return (isValidUser);
    }
   
    // to insert any data use ExecuteNonquery method..
        public int newData(ProductProperties Obj)
    {
        return(row affected or not..)   
    }
    //to display all datas use Dataset.
    public Dataset Alldatas(ProductProperties Obj)
    {
        return (dataset);   
    }
}