Importance of Program.cs

 Example:

var builder = WebApplication.CreateBuilder(args);

// Add services

builder.Services.AddControllers();

builder.Services.AddEndpointsApiExplorer();

builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure middleware

if (app.Environment.IsDevelopment())

{

    app.UseSwagger();

    app.UseSwaggerUI();

}

app.UseHttpsRedirection();

app.UseAuthorization();

app.MapControllers();

app.Run();

This file defines how the app starts, loads middleware, and sets up endpoints.

Understanding Project Folder and File Structure

 Example default structure:

MyFirstApi/

│   Program.cs

│   MyFirstApi.csproj

├── Controllers/

│    WeatherForecastController.cs

├── Properties/

│    launchSettings.json

├── appsettings.json

└── appsettings.Development.json

Program.cs → Application startup configuration.

Controllers/ → Contains API endpoints.

appsettings.json → Configuration file.

launchSettings.json → Environment and profile settings.

Creating a New ASP.NET Core Web API Project

 Using Visual Studio:

1. Open Visual Studio → "Create a new project".

2. Select ASP.NET Core Web API.

3. Configure project name & location.

4. Choose .NET 8 (or latest).

Using Command Line:

dotnet new webapi -n MyFirstApi

cd MyFirstApi

dotnet run

Installing .NET SDK and IDEs

 

Install .NET SDK

• Download from: https://dotnet.microsoft.com/download

• Verify installation: dotnet --version

Choose an IDE

1. Visual Studio (Windows/Mac)

   • Best for beginners & large projects.

2. Visual Studio Code (Cross-platform)

   • Lightweight, flexible.

   • Install C# extension.

Overview of ASP.NET Core and Web API Architecture?

 ASP.NET Core follows a middleware pipeline:

1. Request → Middleware (Authentication, Logging, etc.) → Controller → Response

2. Lightweight, modular design.

3. Built-in dependency injection.

Architecture Diagram:

[Client] → [HTTP Server (Kestrel/IIS)] → [Middleware Pipeline] → [Controller] → [Data Access Layer] → [Database]

Why Use ASP.NET Core for Web APIs?

 ASP.NET Core offers:

• Cross-platform support (Windows, Linux, macOS).

• High performance (among the fastest web frameworks).

• Dependency Injection built-in.

• Unified MVC & API development model.

• Security (Authentication, Authorization, Data Protection).

• Integrated Swagger support for API documentation.

Common Use Cases:

• E-commerce backend APIs.

• Mobile app data services.

• Microservices communication.

• Real-time services with SignalR.

Chapter 1: Introduction and Environment Setup for ASP.NET Core Web API

1. What is a Web API?

2. Why Use ASP.NET Core for Web APIs?

What is a Web API?

A Web API (Application Programming Interface) is a set of endpoints exposed over the web that allow clients (like web apps, mobile apps, or other services) to interact with data or functionality.

Different API Styles

1. REST (Representational State Transfer)

• Uses HTTP methods (GET, POST, PUT, DELETE).

• Data is usually returned in JSON or XML.

• Example:

  GET /api/products

• Best for: Simple, stateless CRUD operations.

2. SOAP (Simple Object Access Protocol)

• Uses XML-based messaging.

• Strict standards, more secure for enterprise needs.

• Example request: <soapenv:Envelope>

      <soapenv:Body>

          <getProductDetails>

              <productId>123</productId>

          </getProductDetails>

      </soapenv:Body>

  </soapenv:Envelope>

3. GraphQL

• Allows clients to request exactly the data they need.

• Single endpoint for all queries/mutations.

• Example:

  graphql
  {
    product(id: "123") {
      name
      price
    }
  }