Working with DELETE Method, Postman Testing, Entity Framework

This article builds on CRUD concepts (GET, POST, PUT, PATCH) and focuses on real-world API development with ASP.NET Core.

1. DELETE Method in ASP.NET Core Web API

What is DELETE?

The DELETE HTTP method is used to remove data from the server.

Real-life example:
Deleting a product from an online store's inventory.

Example Scenario: Delete a Product

Product Model

public class Product
{
    public int Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}

API Code (DELETE)

[HttpDelete("{id}")]
public IActionResult DeleteProduct(int id)
{
    var product = products.FirstOrDefault(p => p.Id == id);
    if (product == null)
        return NotFound();

    products.Remove(product);
    return Ok($"Product with ID {id} deleted");
}

Input (Request)

DELETE /api/products/2

Output (Response)

"Product with ID 2 deleted"

After Deletion – GET Output

[
  { "id": 1, "name": "Laptop", "price": 1200 }
]

2. Testing Web API Using Postman (Step-by-Step)

What is Postman?

Postman is a tool used to test APIs by sending HTTP requests and viewing responses.

Step 1: Open Postman

• Click New → HTTP Request

Step 2: Test GET

• Method: GET

• URL:

https://localhost:5001/api/products

• Click Send
  You will see JSON output.

Step 3: Test POST

• Method: POST

• URL:

https://localhost:5001/api/products

• Body → Raw → JSON

{
  "name": "Keyboard",
  "price": 45
}

• Click Send
  New product is created.

Step 4: Test PUT

• Method: PUT

https://localhost:5001/api/products/1

{
  "name": "Gaming Laptop",
  "price": 1500
}

Step 5: Test PATCH

• Method: PATCH

https://localhost:5001/api/products/1

{
  "price": 1400
}

Step 6: Test DELETE

• Method: DELETE

https://localhost:5001/api/products/1

3. Using Real Database with Entity Framework Core

What is Entity Framework Core?

EF Core is an Object Relational Mapper (ORM) that lets you work with databases using C# classes instead of SQL.

Step 1: Install Packages

dotnet add package Microsoft.EntityFrameworkCore.SqlServer
dotnet add package Microsoft.EntityFrameworkCore.Tools

Step 2: Create DbContext

using Microsoft.EntityFrameworkCore;

public class AppDbContext : DbContext
{
    public AppDbContext(DbContextOptions<AppDbContext> options)
        : base(options) { }

    public DbSet<Product> Products { get; set; }
}

Step 3: Configure in Program.cs

builder.Services.AddDbContext<AppDbContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

Step 4: Controller Using EF Core

[ApiController]
[Route("api/products")]
public class ProductsController : ControllerBase
{
    private readonly AppDbContext _context;

    public ProductsController(AppDbContext context)
    {
        _context = context;
    }

    [HttpGet]
    public IActionResult GetProducts()
    {
        return Ok(_context.Products.ToList());
    }

    [HttpPost]
    public IActionResult AddProduct(Product product)
    {
        _context.Products.Add(product);
        _context.SaveChanges();
        return Ok(product);
    }

    [HttpDelete("{id}")]
    public IActionResult DeleteProduct(int id)
    {
        var product = _context.Products.Find(id);
        if (product == null)
            return NotFound();

        _context.Products.Remove(product);
        _context.SaveChanges();
        return Ok("Deleted successfully");
    }
}

4. Interview-Ready Explanation (With Example)

Q1: What is the difference between GET and POST?

Answer:

• GET retrieves data

• POST sends data to create new records

Example:

• GET /api/products → fetch products

• POST /api/products → add product

Q2: Difference between PUT and PATCH?

Answer:

• PUT updates the entire object

• PATCH updates only specific fields

Q3: When do you use DELETE?

Answer:
DELETE is used to remove a resource permanently from the system.

Example:

DELETE /api/products/5

Q4: Why use Entity Framework Core?

Answer:

• No need to write SQL

• Faster development

• Strongly typed data

• Database-agnostic

Q5: How do you test APIs?

Answer:
Using tools like Postman or Swagger to send HTTP requests and verify responses.

Summary

Feature	Purpose
DELETE	Remove data
Postman	Test APIs
EF Core	Database operations
Interview Prep	Concept clarity