- ELearnHub

1. Introduction to ASP.NET

What is ASP.NET?

ASP.NET is a Microsoft web development framework used to build dynamic, data-driven and interactive web applications using the .NET ecosystem.

Developers can use C# with ASP.NET to implement business logic, interact with databases, process user requests, validate data and create complete web applications.

ASP.NET is not a programming language.

ASP.NET is a web application development framework. C# is a programming language commonly used to build ASP.NET applications.

Major ASP.NET Technologies

Technology	Purpose
Web Forms	Event-driven web application development using .aspx pages and server controls.
MVC	Structured web development using Model, View and Controller.
Web API	Building HTTP-based REST APIs for applications and client applications.

ASP.NET Application Architecture

A typical database-driven ASP.NET application contains several logical layers.

Client → Browser

Presentation Layer → ASP.NET Web Forms / MVC

Business Layer → C# application logic

Data Access Layer → ADO.NET / Entity Framework

Database → SQL Server

Separating responsibilities makes applications easier to understand, maintain, test and extend.

ASP.NET Web Forms

ASP.NET Web Forms is an event-driven framework for creating web applications using pages, server controls and code-behind files.

A Web Forms page normally contains an .aspx file for the user interface and a C# code-behind file for server-side logic.

Example Page Directive

<%@ Page Language="C#"
    AutoEventWireup="true"
    CodeBehind="Default.aspx.cs"
    Inherits="ELearningWebsite.Default" %>

ASP.NET MVC

MVC stands for Model-View-Controller. It separates application data, user interface and request-processing logic into different components.

Model → Data and business representation

View → User interface

Controller → Handles requests and coordinates application operations

ASP.NET Web API

Web API is used to create HTTP-based services that can be consumed by web applications, mobile applications, desktop applications and other systems.

APIs commonly exchange data using JSON.

Example JSON

{
    "studentId": 101,
    "name": "Rahul Kumar",
    "course": "C# Programming"
}

2. ASP.NET Web Forms Fundamentals

Creating a Web Forms Project

An ASP.NET Web Forms application typically contains pages with the .aspx extension and corresponding code-behind files.

Example project structure

Site.master
Default.aspx
Default.aspx.cs
Courses.aspx
Courses.aspx.cs
Web.config

ASP.NET Page Life Cycle

A Web Forms page passes through a sequence of stages during a request.

Page Request
Start
Initialization
Load ViewState
Load PostBack Data
Load
PostBack Event Handling
Rendering
Unload

Page_Load Example

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        // Code executed only during
        // the first page load.
    }
}

Code-Behind

Code-behind allows server-side C# logic to be separated from the HTML and ASP.NET markup.

Default.aspx

<asp:Button
    ID="btnMessage"
    runat="server"
    Text="Click Me"
    OnClick="btnMessage_Click" />

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

Default.aspx.cs

protected void btnMessage_Click(
    object sender,
    EventArgs e)
{
    lblMessage.Text = "Welcome to ASP.NET!";
}

Server Controls

ASP.NET server controls are processed on the server and provide properties, events and server-side functionality.

Control	Purpose
Label	Displays text
TextBox	Accepts user input
Button	Triggers server-side action
DropDownList	Allows selection from a list
CheckBox	Represents a true/false selection
GridView	Displays tabular data

PostBack and IsPostBack

A postback occurs when a page sends a request back to the server, commonly as a result of a server control event.

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        LoadCourses();
    }
}

Why IsPostBack matters: It prevents initialization code such as database binding from running unnecessarily during every postback.

Common Input Controls

TextBox

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

DropDownList

<asp:DropDownList
    ID="ddlCourse"
    runat="server">

    <asp:ListItem>C#</asp:ListItem>
    <asp:ListItem>Python</asp:ListItem>
    <asp:ListItem>SQL</asp:ListItem>

</asp:DropDownList>

CheckBox

<asp:CheckBox
    ID="chkActive"
    runat="server"
    Text="Active Student" />

Validation Controls

ASP.NET validation controls provide a convenient way to validate user input before processing a form.

RequiredFieldValidator

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

<asp:RequiredFieldValidator
    ID="rfvName"
    runat="server"
    ControlToValidate="txtName"
    ErrorMessage="Name is required."
    CssClass="text-danger" />

Important Validation Controls

RequiredFieldValidator
RangeValidator
CompareValidator
RegularExpressionValidator
CustomValidator
ValidationSummary

Master Pages

Master Pages allow common elements such as navigation, headers, footers and site layouts to be shared across multiple Web Forms pages.

Site.Master

<asp:ContentPlaceHolder
    ID="MainContent"
    runat="server">
</asp:ContentPlaceHolder>

Individual content pages then provide their content through the corresponding Content control.

State Management

HTTP is stateless. ASP.NET provides different mechanisms for preserving information between requests.

Technique	Scope
ViewState	Current page
ControlState	Server control state
Session	Individual user
Application	Entire application
Cookies	Client browser
QueryString	URL parameters

Session Example

Session["UserName"] = "Rahul";

string name = Session["UserName"].ToString();

3. Database Programming with ADO.NET

What is ADO.NET?

ADO.NET is a .NET data access technology used to communicate with relational databases.

In an ASP.NET application, ADO.NET can be used to execute SQL commands, retrieve records, insert data, update records and delete data.

Application
↓
ADO.NET
↓
SQL Server

Database Connection

SqlConnection represents a connection to a SQL Server database.

C#

using System.Data.SqlClient;

string connectionString =
    @"Data Source=.;Initial Catalog=StudentDB;
      Integrated Security=True";

using (SqlConnection connection =
       new SqlConnection(connectionString))
{
    connection.Open();

    // Database operations
}

In production applications, connection strings should normally be stored securely in configuration rather than hard-coded into source files.

SqlCommand

SqlCommand is used to execute SQL statements or stored procedures against SQL Server.

string query =
    "SELECT StudentName FROM Students";

using (SqlCommand command =
       new SqlCommand(query, connection))
{
    // Execute command
}

Parameterized SQL should be used when values come from users. Avoid building SQL statements by concatenating raw user input.

SqlDataReader

SqlDataReader provides a fast, forward-only way to read rows returned from a database query.

string query =
    "SELECT StudentID, StudentName FROM Students";

using (SqlCommand command =
       new SqlCommand(query, connection))
using (SqlDataReader reader =
       command.ExecuteReader())
{
    while (reader.Read())
    {
        string name =
            reader["StudentName"].ToString();
    }
}

SqlDataAdapter, DataSet and DataTable

A DataAdapter can populate disconnected data structures such as DataSet and DataTable.

string query =
    "SELECT * FROM Students";

using (SqlDataAdapter adapter =
       new SqlDataAdapter(query, connection))
{
    DataTable table = new DataTable();

    adapter.Fill(table);

    GridView1.DataSource = table;
    GridView1.DataBind();
}

4. DataSource Controls

What are DataSource Controls?

DataSource controls provide a declarative way to connect ASP.NET data-bound controls to data sources.

They can reduce the amount of repetitive data access code required for common database operations.

Common DataSource Controls

SqlDataSource
ObjectDataSource
AccessDataSource
SiteMapDataSource

SqlDataSource

SqlDataSource allows an ASP.NET page to connect to SQL Server and execute configured commands.

ASPX

<asp:SqlDataSource
    ID="dsStudents"
    runat="server"
    ConnectionString="<%$ ConnectionStrings:StudentDB %>"
    SelectCommand="SELECT * FROM Students">
</asp:SqlDataSource>

A connection string can be defined in Web.config using the ConnectionStrings section and referenced from the ASP.NET page.

GridView

GridView is one of the most commonly used ASP.NET Web Forms data-bound controls. It displays records in a tabular format and can support operations such as selection, editing, deleting, paging and sorting.

Basic GridView

<asp:GridView
    ID="GridView1"
    runat="server"
    AutoGenerateColumns="true">
</asp:GridView>

Bind Data

GridView1.DataSource = table;
GridView1.DataBind();

GridView CRUD Operations

GridView can be used with data sources to create database-driven interfaces for viewing and managing records.

Display Data

protected void Page_Load(
    object sender,
    EventArgs e)
{
    if (!IsPostBack)
    {
        LoadStudents();
    }
}

private void LoadStudents()
{
    // Retrieve records from database
    // and bind them to GridView.
}

Delete Example

protected void GridView1_RowDeleting(
    object sender,
    GridViewDeleteEventArgs e)
{
    int studentId =
        Convert.ToInt32(
            GridView1.DataKeys[e.RowIndex].Value);

    // Execute parameterized DELETE query.
}

Always validate and authorize database operations. A delete button in the user interface should not be treated as sufficient protection for destructive operations.

GridView Paging and Sorting

Paging prevents large numbers of records from being displayed on a single page.

Enable Paging

<asp:GridView
    ID="GridView1"
    runat="server"
    AllowPaging="true"
    PageSize="10"
    AllowSorting="true">

</asp:GridView>

For very large datasets, efficient server-side paging is preferable to loading every record into memory.

5. ASP.NET MVC

MVC Architecture

MVC separates an application into three primary components.

Model
Represents application data and domain logic.

View
Presents information to the user.

Controller
Receives requests and coordinates application logic.

Typical Request Flow

Browser → Controller → Model / Database → Controller → View → Browser

Model

A model represents data used by the application.

Student.cs

public class Student
{
    public int StudentID { get; set; }

    public string StudentName { get; set; }

    public int Age { get; set; }

    public string City { get; set; }
}

View

A View is responsible for presenting information to the user.

Razor View Example

@model Student

<h2>Student Details</h2>

<p>
    Name: @Model.StudentName
</p>

<p>
    City: @Model.City
</p>

The MVC example above uses Razor syntax and is separate from the Web Forms .aspx syntax used in the earlier sections.

Controller

Controllers receive requests, execute appropriate application logic and return a response.

StudentController

public class StudentController
    : Controller
{
    public ActionResult Index()
    {
        return View();
    }
}

Routing

Routing maps an incoming URL to an appropriate controller action.

Example URL

/Student/Details/10

This could map to a Details action of StudentController with an ID value of 10.

Model Validation

MVC applications can use data annotation attributes to define validation rules on models.

public class Student
{
    public int StudentID { get; set; }

    [Required]
    public string StudentName { get; set; }

    [Range(18, 60)]
    public int Age { get; set; }
}

Validation should be enforced on the server even when client-side validation is also enabled.

6. ASP.NET Web API

What is a REST API?

A REST-style API exposes resources through HTTP endpoints and uses standard HTTP methods to perform operations.

Method	Typical Purpose
GET	Retrieve data
POST	Create a resource
PUT	Update a resource
DELETE	Delete a resource

HTTP Methods

Web APIs use HTTP requests to communicate with clients. Each HTTP method communicates the intended type of operation.

GET → Read

POST → Create

PUT → Update

DELETE → Remove

GET Request

A GET endpoint returns information to the client.

Example

[HttpGet]
public IEnumerable<Student> GetStudents()
{
    return students;
}

Example Endpoint

GET /api/students

POST Request

POST is generally used to create a new resource.

[HttpPost]
public IHttpActionResult CreateStudent(
    Student student)
{
    // Save student.

    return Ok(student);
}

PUT and DELETE

PUT

[HttpPut]
public IHttpActionResult UpdateStudent(
    int id,
    Student student)
{
    // Update student.

    return Ok();
}

DELETE

[HttpDelete]
public IHttpActionResult DeleteStudent(
    int id)
{
    // Delete student.

    return Ok();
}

JSON in Web API

JSON is commonly used to represent structured data exchanged between APIs and clients.

{
    "studentID": 101,
    "studentName": "Rahul Kumar",
    "age": 21,
    "city": "Delhi"
}

A frontend application can send JSON to an API and receive JSON in response.

7. Practical Project — Student Management System

Project Objective

Build a database-driven Student Management System that demonstrates the major technologies covered in this course.

Core Features

Add new students.
Display students in GridView.
Edit student records.
Delete student records.
Search students.
Validate form input.
Store records in SQL Server.
Use Master Page for common layout.
Implement database access using ADO.NET.
Expose student information through an API.

Suggested Database

CREATE TABLE Students
(
    StudentID INT PRIMARY KEY IDENTITY(1,1),

    StudentName VARCHAR(100) NOT NULL,

    Email VARCHAR(150) UNIQUE,

    Age INT CHECK (Age >= 18),

    City VARCHAR(50),

    Course VARCHAR(100),

    IsActive BIT DEFAULT 1
);

Final Application Architecture

The completed project can be organized into multiple layers and interfaces.

Web Forms Application
Student Registration
Student List
GridView CRUD

↓

Business Logic
Validation
Application Rules

↓

Data Access
ADO.NET
SqlConnection
SqlCommand
SqlDataReader

↓

SQL Server
Students Table

Extension — MVC Version

The same Student Management System can then be recreated using MVC to understand how the same business requirement can be implemented using a different architectural pattern.

Extension — Web API Version

Finally, expose student records through REST endpoints so that another application can retrieve, create, update and delete student information through HTTP.

Final Learning Outcome

After completing this course, a learner should be able to understand the fundamentals of ASP.NET Web Forms, develop server-side applications using C#, connect applications to SQL Server, display and manage data using GridView, implement validation and state management, understand MVC architecture, and build basic REST-style Web APIs.

Practice Challenges

Beginner

Create a Web Forms registration form.
Add TextBox, DropDownList and CheckBox controls.
Add validation controls.
Create a Master Page.
Create three content pages.

Intermediate

Create a Student database.
Connect ASP.NET to SQL Server.
Display records using GridView.
Implement insert, update and delete.
Add search, sorting and paging.

Advanced

Build the Student Management System.
Create an MVC version of the application.
Create REST API endpoints.
Return student information as JSON.
Connect a client application to the API.

Course Summary

ASP.NET provides a complete ecosystem for building database-driven web applications. In this course, you explored both the fundamentals and practical application-development concepts.

ASP.NET fundamentals
Web Forms and code-behind
Page life cycle and postback
Server controls
Validation controls
Master Pages
State management
ADO.NET
SqlConnection and SqlCommand
SqlDataReader and DataAdapter
DataSource controls
GridView
GridView CRUD
Paging and sorting
MVC architecture
Models, Views and Controllers
MVC routing and validation
REST APIs
HTTP methods
JSON
Student Management System

Recommended Learning Approach: Do not only read the examples. Create the project, type the code yourself, connect it to SQL Server, introduce small changes, intentionally test invalid input, and build the final Student Management System from the individual concepts.

Learn. Grow. Succeed.

ASP.NET Web Development

1. Introduction to ASP.NET

What is ASP.NET?

Major ASP.NET Technologies

ASP.NET Application Architecture

ASP.NET Web Forms

ASP.NET MVC

ASP.NET Web API

2. ASP.NET Web Forms Fundamentals

Creating a Web Forms Project

ASP.NET Page Life Cycle

Code-Behind

Server Controls

PostBack and IsPostBack

Common Input Controls

Validation Controls

Important Validation Controls

Master Pages

State Management

3. Database Programming with ADO.NET

What is ADO.NET?

Database Connection

SqlCommand

SqlDataReader

SqlDataAdapter, DataSet and DataTable

4. DataSource Controls

What are DataSource Controls?

Common DataSource Controls

SqlDataSource

GridView

GridView CRUD Operations

Display Data

Delete Example

GridView Paging and Sorting

5. ASP.NET MVC

MVC Architecture

Typical Request Flow

Model

View

Controller

Routing

Model Validation

6. ASP.NET Web API

What is a REST API?

HTTP Methods

GET Request

POST Request

PUT and DELETE

JSON in Web API

7. Practical Project — Student Management System

Project Objective

Core Features

Suggested Database

Final Application Architecture

Extension — MVC Version

Extension — Web API Version

Practice Challenges

Beginner

Intermediate

Advanced

Course Summary