Curriculum
Introduction to Web APIs is one of the most important topics in modern software development. Today, applications rarely work in isolation. Mobile applications, web applications, desktop applications, IoT devices, cloud services, and third-party platforms communicate with each other through APIs. Understanding Introduction to Web APIs is essential because Web APIs serve as the backbone of modern distributed systems and cloud-based applications.
ASP.NET Core provides a powerful framework for building scalable, secure, and high-performance Web APIs. Whether you are developing mobile applications, e-commerce platforms, banking systems, ERP software, CRM solutions, SaaS products, or microservices, Web APIs are a fundamental technology.
API stands for:
Application
Programming
InterfaceAn API is a mechanism that allows different software applications to communicate with each other.
Example:
Application A
↓
API
↓
Application BThe API acts as a bridge between systems.
A Web API is an API that communicates over the internet using HTTP.
Example:
Mobile App
↓
Web API
↓
DatabaseThe API receives requests and returns responses.
Modern applications require:
Data Sharing
Remote Access
Cross-Platform Communication
System IntegrationWeb APIs make this possible.
Food Delivery Application:
Mobile App
↓
Restaurant API
↓
Order DatabaseThe mobile application communicates through APIs.
Examples:
Mobile Apps
Web Applications
Banking Systems
E-Commerce Platforms
Social Media Platforms
Cloud ServicesWeb APIs are used everywhere.
Workflow:
Client Request
↓
Web API
↓
Business Logic
↓
Database
↓
ResponseThe API processes requests and returns data.
Client:
Browser
Mobile App
Desktop ApplicationServer:
Web API ApplicationThe client consumes API services.
Request:
Get Student DataResponse:
{
"id": 1,
"name": "Rahul"
}Data is exchanged between systems.
HTTP stands for:
HyperText Transfer ProtocolHTTP is the communication protocol used by Web APIs.
Benefits:
Standard Protocol
Internet Compatible
Widely SupportedMost APIs use HTTP.
A client sends:
RequestExample:
Get Student InformationThe API receives and processes the request.
The server sends:
ResponseExample:
{
"student":
"Rahul"
}The response contains requested data.
An Endpoint is a URL exposed by the API.
Example:
/api/studentsClients access resources through endpoints.
Student API:
/api/students
/api/courses
/api/teachersEach endpoint represents a resource.
JSON stands for:
JavaScript Object NotationJSON is the most common API data format.
Example:
{
"id": 1,
"name": "Rahul",
"course": ".NET"
}JSON is lightweight and easy to read.
Benefits:
Readable
Lightweight
Cross-Platform
Easy ParsingMost modern APIs use JSON.
Web APIs use HTTP methods to perform operations.
Common methods:
GET
POST
PUT
DELETEThese methods define request behavior.
Purpose:
Retrieve DataExample:
Get Student ListGET does not modify data.
Purpose:
Create DataExample:
Add New StudentPOST creates new records.
Purpose:
Update DataExample:
Update Student InformationPUT modifies existing resources.
Purpose:
Remove DataExample:
Delete Student RecordDELETE removes resources.
Resources represent application data.
Examples:
Students
Teachers
Courses
Orders
ProductsResources are exposed through endpoints.
Most APIs today follow:
RESTREST stands for:
Representational
State
TransferREST is the most popular API architecture style.
Stateless
Client-Server
Resource-Based
HTTP DrivenThese characteristics improve scalability.
Meaning:
Each Request
Contains Everything NeededThe server does not store session information.
ASP.NET Core provides:
Controllers
Routing
Model Binding
JSON Serialization
AuthenticationThese features simplify API development.
Example:
[ApiController]
public class
StudentController :
ControllerBase
{
}API controllers handle HTTP requests.
Benefits:
Lightweight
API Focused
No View SupportWeb APIs generally use ControllerBase.
Example:
return Ok(
students);Response:
HTTP 200 OKThe client receives the requested data.
Success:
200 OKCreated:
201 CreatedBad Request:
400 Bad RequestUnauthorized:
401 UnauthorizedNot Found:
404 Not FoundServer Error:
500 Internal Server ErrorStatus codes indicate request results.
Client
↓
API Controller
↓
Service Layer
↓
Repository
↓
DatabaseThis architecture is common in enterprise applications.
Student Management System API:
/api/students
/api/teachers
/api/courses
/api/resultsApplications consume these endpoints.
Endpoints:
/api/products
/api/orders
/api/customers
/api/paymentsAll business operations are exposed through APIs.
Endpoints:
/api/accounts
/api/transactions
/api/transfersWeb APIs power financial systems.
Works with any client.
Supports large systems.
Multiple applications use the same API.
Connects different systems.
Works well in modern architectures.
These benefits make APIs essential.
Creates confusion.
Reduces API quality.
Complicates client development.
Creates security risks.
Makes APIs difficult to use.
An API allows software applications to communicate with each other.
A Web API communicates over HTTP and exposes application functionality.
JSON is a lightweight data-interchange format commonly used in APIs.
REST is an architectural style for building web services.
GET, POST, PUT, and DELETE are common HTTP methods.
They enable communication between different systems and applications.
A Web API is a service that allows applications to communicate over HTTP.
JSON is a lightweight format used to exchange data between systems.
REST is an architectural style used to build scalable web services.
HTTP Methods define operations such as GET, POST, PUT, and DELETE.
Web APIs enable communication, integration, and data sharing between systems.
It provides the foundation for modern web development, mobile applications, cloud services, and microservices.