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I have been trying to find the different between MVC and 3-tier architecture in ASP.NET. I referred to some previous some previous questions and some pages, but could find a clear answer.
Here is a a msdn page about MVC implementation: http://msdn.microsoft.com/en-us/library/ff647462.aspx
Consider, I ahve this code:
Single page aspx UI and code as well
<%@ Import Namespace="System.Data" %>
<%@ Import Namespace="System.Data.SqlClient" %>
<html>
<head>
<title>start</title>
<script language="c#" runat="server">
void Page_Load(object sender, System.EventArgs e)
{
String selectCmd = "select * from Recording";
SqlConnection myConnection =
new SqlConnection(
"server=(local);database=recordings;Trusted_Connection=yes");
SqlDataAdapter myCommand = new SqlDataAdapter(selectCmd,
myConnection);
DataSet ds = new DataSet();
myCommand.Fill(ds, "Recording");
recordingSelect.DataSource = ds;
recordingSelect.DataTextField = "title";
recordingSelect.DataValueField = "id";
recordingSelect.DataBind();
}
</script>
</head>
<body>
<asp:dropdownlist id="recordingSelect" runat="server" />
<asp:button runat="server" text="Submit" OnClick="SubmitBtn_Click" />
</form>
</body>
</html>
Now, consider I have different files for
---- View and Code-behind spearated ----
.aspx
<%@ Page language="c#" Codebehind="Solution.aspx.cs"
AutoEventWireup="false" Inherits="Solution" %>
<html>
<asp:dropdownlist id="recordingSelect" runat="server" />
</form>
</body>
</html>
.aspx.cs
using System;
using System.Data;
using System.Data.SqlClient;
public class Solution : System.Web.UI.Page
{
private void Page_Load(object sender, System.EventArgs e)
{
if(!IsPostBack)
{
String selectCmd = "select * from Recording";
SqlConnection myConnection =
new SqlConnection(
"server=(local);database=recordings;Trusted_Connection=yes");
SqlDataAdapter myCommand = new SqlDataAdapter(selectCmd, myConnection);
DataSet ds = new DataSet();
myCommand.Fill(ds, "Recording");
recordingSelect.DataSource = ds;
recordingSelect.DataTextField = "title";
recordingSelect.DataValueField = "id";
recordingSelect.DataBind();
}
}
Controller class, I am not able to discern the difference between the business logic (that would have been similar for a middle tier in a 3 tier architecture) and the controller.
612
Conceptually the three-tier architecture is linear. However, the [model-view-controller] MVC architecture is triangular: the view sends updates to the controller, the controller updates the model, and the view gets updated directly from the model. The MVC architecture is not necessarily triangular, it can be either.
MVC abstracts away the details of how the architecture of an app is implemented. N-tier just refers to the physical structure of an implementation. These two are sometimes confused because an MVC design is often implemented using an N-tier architecture.
MVC pattern architecture is basically a three-layered architecture. It separates the characteristics of application. Its first layer is related to the user input logic, second layer is related to the business logic and third layer is used to implement user interface logic.
The business logic layer in a three-tier application consists of components that implement business rules, centralizing business logic, and separating it from the user interface and data access. The business logic tier simplifies maintenance and integration of new components.
I actually strugled with this a while myslef, there are different philosophies on how to implement it correctly, so this is how I understand it in my own words how I understand the relation between the different things involved (Models/Views/Controllers/Business Logic):
Model instances that come from the controllerI have seen other approaches where the business logic is actually put into the controllers, but in my eyes that defeats the purpose. We are not building MVC applications to have a nice structure, but also to be able to perform unit test better.
Getting back to your question, how does it all relate to ASP.NET 3-tier architecture.
One could say that basically the entire MVC web application is nothing more the Presentation layer (+ wireing up the Presentation layer with the Busines layer).
The other layers stay separate and independent from the presentation layer, as they should have before.
157
MVC and 3-tier are completely different things.
I see a lot of people confuse the two because both got 3 parts.
MVC is a UI pattern:
View: contains html and js only (in case of a web project)
Controller: is a kind of a mediator between the UI (= the view) and the back-end (= the model)
Model: this is where your domain objects live, as well as the business and data-access logic
3-tier concerns the whole of you application:
UI: contains the html/js as well as the code behind of the pages.
There is absolutely no logic here, other than UI code and calling the business layer.
Business layer: this is where you put things like calculations, conditions, validation, ..
So the actual behaviour of your application. There is no data access code here.
Data access: here where you talk to the database and return the data to the business layer.
Nothing else, the business layer should know what to do with it.
So if you combine the two, you'll get:
UI: views and controllers
Business layer: part of the model
Data access: part of the model
Domain object: you'll want to put the objects you're working with (product, order, ..) in a separate layer.
This is also a part of the model.
Shoot if you got questions!
20
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