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?