Unit 01

CLR (Common Language Runtime) is the execution engine of the .NET Framework. It manages the execution of .NET programs and provides several important services.

Main Services of CLR

ASP.NET is a server-side web development framework used to build dynamic and interactive web applications. Its important features are:

• 01Server-Side Technology — ASP.NET code runs on the server and generates HTML that is sent to the browser.
• 02Compiled — ASP.NET applications are compiled, providing better performance than interpreted scripting.
• 03Rich Server Controls — Provides ready-made controls such as TextBox, Button, GridView, etc.
• 04State Management — Supports ViewState, Session, Cookies, and Application objects to maintain data between requests.
• 05Security — Provides built-in authentication and authorization features.
• 06Database Integration — Supports database access through ADO.NET, LINQ, and Entity Framework.
• 07Easy Configuration and Debugging — Uses Web.config and provides debugging support through Visual Studio.
• 08Master Pages — Allows a common layout and consistent appearance across multiple pages.

FCL (Framework Class Library) is a large collection of pre-built and reusable classes, methods, and libraries provided by the .NET Framework. It helps developers perform common programming tasks without writing the functionality from scratch.

Examples of FCL Classes / Libraries

Advantages

• 01Reduces repetitive coding.
• 02Provides ready-made functionality.
• 03Makes application development faster and easier.

The .NET Framework is a software framework developed by Microsoft for developing and executing applications. It provides a common runtime environment for programs written in different .NET languages.

Main Components

The Code Behind model is an ASP.NET programming model in which the user interface (UI) and programming logic are separated into two files:

Example

Default.aspx:

<asp:Button ID="btn1" runat="server"
    Text="Click Me" OnClick="btn1_Click" />
<asp:Label ID="lbl1" runat="server" />

Default.aspx.cs:

protected void btn1_Click(object sender, EventArgs e)
{
    lbl1.Text = "Hello!";
}

ViewState is a state-management mechanism in ASP.NET used to preserve the values of controls between postbacks. It stores the state of page and control properties in a hidden field on the page.

Purpose of ViewState

• 01Maintains control values when the page is submitted and reloaded.
• 02Helps preserve the state of controls between postbacks.
• 03Allows ASP.NET pages to retain their previous values without storing them on the server.

Example

<asp:TextBox ID="txtName" runat="server" />

If the user enters a value and the page performs a postback, ViewState helps preserve the entered value.

The .NET Framework is a software framework that provides a common environment for developing and executing applications written in different .NET languages. Its architecture allows different languages to work together using common runtime and type-system rules.

Architecture Diagram

.NET Languages
┌──────────────────────┐
│ C# │ VB.NET │ Other  │
└──────────┬───────────┘
           ↓
   ┌─────────────────┐
   │      CLS         │
   │ Common Language  │
   │ Specification    │
   └────────┬─────────┘
            ↓
   ┌─────────────────┐
   │      CTS         │
   │ Common Type      │
   │ System           │
   └────────┬─────────┘
            ↓
   ┌─────────────────┐
   │      FCL         │
   │ Framework Class  │
   │ Library          │
   └────────┬─────────┘
            ↓
   ┌─────────────────┐
   │      CLR         │
   │ Common Language  │
   │ Runtime          │
   └────────┬─────────┘
            ↓
      Operating System

Compilation Flow

Source Code
     ↓
Language Compiler
     ↓
MSIL / CIL
     ↓
CLR (JIT Compiler)
     ↓
Native Machine Code
     ↓
Execution

The ASP.NET Page Life Cycle is the sequence of stages through which an ASP.NET page passes from the time it is requested by the browser until the response is sent back. Each stage provides specific events that can be used to initialize controls, handle events, save state, and generate the final HTML.

Page Life Cycle Diagram

Page Request
     ↓
  PreInit
     ↓
   Init
     ↓
InitComplete
     ↓
LoadViewState
     ↓
LoadPostData
     ↓
   Load
     ↓
PostBack Events
     ↓
LoadComplete
     ↓
 PreRender
     ↓
SaveStateComplete
     ↓
  Render
     ↓
 Unload

Main Stages

PostBack is the process in which an ASP.NET web page submits data back to the server for processing. The request is generally sent back to the same page (same URL). It commonly occurs when the user performs an action such as clicking a Button or changing a control value.

Working of PostBack

User opens ASP.NET Page
       ↓
  Page displayed
       ↓
User performs action
 (e.g. Button Click)
       ↓
   HTTP POST
       ↓
Same page sent to Server
       ↓
Server processes event
       ↓
Response sent to Browser

Example

<asp:Button ID="btnSubmit"
    runat="server"
    Text="Submit"
    OnClick="btnSubmit_Click" />

<asp:Label ID="Label1" runat="server" />

Code-behind:

protected void btnSubmit_Click(object sender, EventArgs e)
{
    Label1.Text = "Button clicked!";
}

When the button is clicked, the page is submitted to the server and the btnSubmit_Click event is executed.

IsPostBack

ASP.NET provides the IsPostBack property to determine whether the page is being loaded for the first time or because of a postback:

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        Label1.Text = "Welcome!";
    }
}

IsPostBack = false → First time the page loads. IsPostBack = true → Page has been submitted back to the server.

Difference between CTS and CLS