3-Tier Architecture in ASP.NET with C# tutorial

   

In 3 tier programming architecture, the application development is broken into three main parts; these are: Presentation layer(PL), Business Acess Layer(BAL) and Data Access Layer(DAL). These separations ensure independent development of those layers such that a change in one does not affect the other layers. For instance a change in the logic of the DAL layer does not affect the the BAL nor the presentation layer. It also makes testing easier in that a whole layer can be replaced with a stub object.

 For example instead of testing the whole application with an actual connection to database, the DAL can be replaced with a stub DAL for testing purposes. The DAL deals with actual database operations. These operations are inserting, updating, deleting and viewing. The BAL deals with the business logic for a particular operation. The PL has the user controls for interacting with the application.

3-Tier programming architecture also enables re-use of code and provides a better way for multiple developers to work on the same project simultaneously.

1. Start a new website project
2. Design you page as shown below,
   
3. Add sub-folders and class objects within the App_code folder as shown below,
   
4. Code for the add button is shown below,
   protected void cmdAdd_Click(object sender, EventArgs e)
{
    CustomerBAL cBal = new CustomerBAL();
    try
    {
        if (cBal.Insert(txtCustomerID.Text, txtFirstName.Text, txtLastName.Text) > 0)
        {
            lblMessageLine.Text = "Record inserted successfully.";
        }
        else
        {
            lblMessageLine.Text = "Record not inserted.";
        }
    }
    catch (Exception ex)
    {
        lblMessageLine.Text = ex.Message;
    }
    finally
    {
        cBal = null;
    }
} 
5. code for CustomerBAL.cs
   using System;
   using System.Collections.Generic;
   using System.Web;
   ///
   
   /// Summary description for CustomerBAL
   ///
   
   public class CustomerBAL
   {
       public CustomerBAL()
       {
           //
           // TODO: Add constructor logic here
           //
       }
       public int Insert(string CustomerID, string FirstName, string LastName)
       {
           CustomerDAL cDal=new CustomerDAL();
           try
           {
               return cDal.Insert(CustomerID, FirstName, LastName);
           }
           catch
           {
               throw;
           }
           finally
           {
               cDal = null;
           }
       }
   } 
6. Code for CustomerDAL.cs
   using System;
   using System.Collections.Generic;
   using System.Web;
   using System.Data.SqlClient;
   using System.Data;
   
   ///
   
   /// Summary description for CustomerDAL
   ///
   
   public class CustomerDAL
   {
       public CustomerDAL()
       {
           //
           // TODO: Add constructor logic here
           //
       }
       public int Insert(string CustomerID, string FirstName, string LastName)    public int Insert(string CustomerID, string FirstName, string LastName)
       {
           //declare SqlConnection and initialize it to the settings in the section of the web.config
           SqlConnection Conn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["dbConnectionString"].ConnectionString);
           //===============================
           //prepare the sql string
           string strSql = "insert into t_Customers(CustomerID,FirstName,LastName) ";
           strSql = strSql + "values(@CustomerID,@FirstName,@LastName)";
   
           //declare sql command and initalize it
           SqlCommand Command = new SqlCommand(strSql, Conn);
   
           //set the command type
           Command.CommandType = CommandType.Text;
   
           try
           {
               //define the command parameters
               Command.Parameters.Add(new SqlParameter("@CustomerID", SqlDbType.VarChar));
               Command.Parameters["@CustomerID"].Direction = ParameterDirection.Input;
               Command.Parameters["@CustomerID"].Size = 20;
               Command.Parameters["@CustomerID"].Value = CustomerID;
   
               Command.Parameters.Add(new SqlParameter("@FirstName", SqlDbType.VarChar));
               Command.Parameters["@FirstName"].Direction = ParameterDirection.Input;
               Command.Parameters["@FirstName"].Size = 25;
               Command.Parameters["@FirstName"].Value = FirstName;
   
               Command.Parameters.Add(new SqlParameter("@LastName", SqlDbType.VarChar));
               Command.Parameters["@LastName"].Direction = ParameterDirection.Input;
               Command.Parameters["@LastName"].Size = 25;
               Command.Parameters["@LastName"].Value = LastName;
   
               //open the database connection
               Conn.Open();
               //execute the command
               return Command.ExecuteNonQuery();
           }
           catch
           {
               throw;
           }
           finally
           {
               Command.Dispose();
               Conn.Dispose();
           }
       }
   }
7. Set the connection string on the web.config file
8. Run the project