ProducsController.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using WebApplication21.Data;
using WebApplication21.Models;

namespace WebApplication21.Controllers
{
    [Route("api/[controller]")]
    public class ProductsController : ControllerBase
    {
        private readonly ProductsDbContext _db;

        public ProductsController(ProductsDbContext db)
        {
            _db = db;
        }

        [HttpGet("{id}")]
        public IActionResult Get(int id)
        {
            var product = _db.Products.SingleOrDefault(p => p.Id == id);

            if (product == null)
            {
                return NotFound();
            }

            return Ok(product);
        }

        [HttpGet]
        public List<Product> GetAll() => _db.Products.ToList();

        [HttpPost]
        public IActionResult Create([FromBody] Product product)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            _db.Add(product);
            _db.SaveChanges();

            return CreatedAtAction(nameof(Get), new { id = product.Id }, product);
        }

        [HttpPut]
        public IActionResult Update([FromBody] Product product)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            _db.Update(product);
            _db.SaveChanges();

            return NoContent();
        }

        [HttpDelete("{id}")]
        public IActionResult Delete(int id)
        {
            var product = Get(id);

            if (product == null)
            {
                return NotFound();
            }

            _db.Remove(product);
            _db.SaveChanges();

            return NoContent();
        }
    }
}