Getting Started with ASP.NET Core Web API: A Beginner's Guide

Introduction

In this blog, you’ll learn how to create a simple ASP.NET Core Web API from scratch using Visual Studio. This step-by-step guide is perfect for beginners looking to understand how RESTful APIs work.

What is a Web API?

A Web API(Application Programming Interface) allows different applications to communicate with each other over HTTP and is used to build RESTful services.

Why do we use ASP.NET Core Web API?

Cross-platform(Platform Independent)
Supports DI(Depenency Injection)
Supports OpenAI(Swagger)

Prerequisites

Basic knowledge of C# and SQL
.NET SDK
Familiar with Visual Studio IDE

Creating your first Web API project

Step 1

Open Visual Studio
Create a new project
Select the ASP.NET Core Web API template

Step 2

Name it EmployeeManagement
Choose the latest .NET version
Click Create

Understanding the Code Structure

Program.cs: Entry point for application
Controllers: Contains API controllers
Models: Contains business logic
appsettings.json: Configuration file

DbContext Setup with SQL Server

To make your API data persistent, you can connect it to a SQL Server database using Entity Framework Core.
First, install the required EF Core packages that support SQL Server. Then, create a class called EmployeeDbContext that manages database access and maps your Employee model to a database table.
Next, register this DbContext in the application’s services so that it can be used in the controller. You'll also add a connection string in the configuration file (appsettings.json) to define how the app connects to SQL Server.

CRUD Operations for Employee

Create the Model: Models/Entities/Employee.cs.

CRUD Operations

Create the Controller: Controllers/EmployeesController.cs

1. GET – Get All Employees & Get by ID

These two methods handle the retrieval of employee data.

The first method [HttpGet] returns a full list of employees with an HTTP 200 OK response.
The second method [HttpGet("{id}")] retrieves a specific employee by ID.

HTTP 200

2. POST – Add a New Employee

This method handles employee creation.

The [HttpPost] method accepts an Employee object from the request body.
It adds the employee to the database.

Employee object

3. PUT – Update an Existing Employee

This method updates the details of an existing employee

The [HttpPut("{id}")] method checks if an employee with the given ID exists.
It updates the employee’s name, department, phone, and salary.

ID exists

4. DELETE – Remove an Employee

This method deletes an employee based on the provided ID.

The [HttpDelete("{id}")] method searches for the employee.
If the employee exists, it removes them from the list.

Remove an Employee

Testing with Swagger

https://localhost:{port}/swagger/index.html

You can test all GET, POST, PUT, and DELETE requests directly from the Swagger interface.

Swagger interface

Conclusion

In this blog, you learned how to build a simple yet functional Employee Management Web API using ASP.NET Core. We covered how to create models, set up controllers, implement CRUD operations, and connect to a SQL Server database using Entity Framework Core.

Source Code

You can find the complete source code for this project on GitHub using the link below.

GitHub Repo: https://github.com/Vinay-Reddy-Thadakala/EmployeeManagement