This document provides an overview of implementing a 3-tier architecture in ASP.NET using C#. It describes the 3 tiers - presentation layer, business logic layer, and data access layer. The presentation layer handles user input/output. The business logic layer contains application logic and communicates with the data access layer. The data access layer connects to the database and performs CRUD operations. The document outlines setting up the project structure with App_Code/BusinessLayer and App_Code/DataAccessLayer folders and creating sample BusinessLogic and DataAccess classes.

1. In this asp.net tutorial you will learn how to implement 3-tier architecture in asp.net
using c#. 3-Tier architecture is also called layered architecture. Some people called it n-tier
architecture. Layer architectures are essentially objects and work in object oriented environment
just like asp.net. 3-tier architecture is a very well known architecture in the world of software
development, it doesn't matter whether you are developing web based application or desktop
based, it is the best architecture to use.
3-Tier Architecture in asp.net using c#
3-Tier architecture consists of
1) UI or Presentation Layer
2) Business Access Layer or Business Logic Layer
3) Data Access Layer
Presentation Layer
Presentation layer consists of pages like .aspx or desktop based form where data is presented to
users or getting input from users.
Business Logic layer or Business Access Layer
Business logic layer contains all of the business logic. Its responsibility is to validate the business
rules of the component and communicating with the Data Access Layer. Business Logic Layer is
the class in which we write functions that get data from Presentation Layer and send that data to
database through Data Access Layer.
Data Access Layer

2. Data Access Layer is also the class that contains methods to enable business logic layer to
connect the data and perform desired actions. These desired actions can be selecting, inserting,
updating and deleting the data. DAL accepts the data from BAL and sends it to the database or
DAL gets the data from the database and sends it to the business layer. In short, its
responsibility is to communicate with the backend structure.
Illustration of 3-Tier Architecture with Diagram
The figure clearly describe about the purpose of BAL and DAL. The main advantage of 3-tier
architecture is to separate the presentation layer from data access layer. You will not write any
function to communicate with database in presentation layer, all the required functions for
communication with database will be available in DataAcessLayer. Its mean at presentation layer
you will just focus at information that you will present in front of user.
I am going to create BAL, DAL in App_Code folder. You can also create separate projects for
BAL, DAL and UI (Your website) and referenced your DAL into BAL and BAL into UI. In that
scenario you have to rebuild the DAL and BAL every time, in order to view the change that you
have made in your BAL and DAL. So to get rid of rebuilding layers every time after change, I am
going to create BAL and DAL folder in App_Code. Now feel free to make changes in BAL and DAL
and just refresh the webpage to view the change that you made, in short no rebuilding of DAL
and BAL is required. The following figure shows the 3-tier architecture of our website that we are
going to made.

3. Design and implement 3-tier architecture
.
1) Open visual studio or visual web developer.
2) Go to File-> New Web Site
3) Select ASP.NET Web Site and then browse the Folder in which you want to save your web
pages.

4. 4) Go to Solution Explorer and then right click on your website folder.
Go to Add ASP.NET Folder-> App_Code.
5) Now right click on App_Code Folder and select New Folder.
6) Create Two Folders and give BusinessLayer and DataAccessLayer names to them.

5. 7) Now right click on DataAccessLayer -> Add New Item.
8) Select Class as template and give DbAccess name to that class.
9) Now right click on BusinessLayer folder-> Add New Item

6. 10) Select Class as template and give BusComments.cs name to that class.
Now open your DbAccess.cs file placed in DataAccessLayer folder. Clear it by deleting all its builtin code and then copy/paste the following code in your DbAccess.cs file and then save it

7. 10) Select Class as template and give BusComments.cs name to that class.
Now open your DbAccess.cs file placed in DataAccessLayer folder. Clear it by deleting all its builtin code and then copy/paste the following code in your DbAccess.cs file and then save it