ASPNetCore/TestAppRuna/API/CartController.cs

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Threading.Tasks;
using TestAppRuna.Entities;
using TestAppRuna.Services;

namespace TestAppRuna.API
{
    [Route("api/[controller]")]
    [ApiController]
    public class CartController : ControllerBase
    {
        public ICartService CartSvc { get; }

        public CartController(ICartService cartSvc)
        {
            this.CartSvc = cartSvc;
        }


        [HttpGet]
        public async Task<ActionResult<List<CartCustomerListItem>>> Get()
        {
            return await CartSvc.Get();
        }
        [HttpGet("{customerId}")]
        public async Task<ActionResult<List<CartListItem>>> GetFromCustomer(Guid customerId)
        {
            return await CartSvc.GetFromCustomer(customerId);
        }
        [HttpPost]
        public async Task<ActionResult<bool>> Post([FromBody] CartCreateUpdateModel model)
        {
            if (await CartSvc.HasCustomerID(model.CustomerID))
            {
                ModelState.AddModelError("CustomerID", "Customer ID not found");
            }
            if(await CartSvc.HasProductID(model.ProductID))
            {
                ModelState.AddModelError("ProductID", "Product ID not found");
            }
            
            if(ModelState.IsValid == false)
            {
                return BadRequest(ModelState);
            }

            return await CartSvc.CreateOrUpdateCart(model);
        }

        [HttpPost("delete")]
        public async Task<ActionResult<bool>> Delete([FromBody] CartDeleteModel model)
        {
            var success = await CartSvc.DeleteCart(model);
            if(success == false)
            {
                return NotFound();
            } else
            {
                return true;
            }
        }
    }
    public class CartListItem { 
        public Guid ProductID { get; set; }
        public string ProductName { get; set; }
        public decimal ProductPrice { get; set; }
        public int Quantity { get; set; }
    }
    public class CartCustomerListItem
    {
        public Guid ProductID { get; set; }
        public string ProductName { get; set; }
        public decimal ProductPrice { get; set; }
        public string CustomerName { get; set; }
        public string CustomerEmail { get; set; }
        public int Quantity { get; set; }
    }
    public class CartCreateUpdateModel
    {
        [Required]
        public Guid CustomerID { get; set; }
        [Required]
        public Guid ProductID { get; set; }
        [Required]
        [Range(1,Double.MaxValue)]
        public int Quantity { get; set; }
    }
    public class CartDeleteModel
    {
        [Required]
        public Guid CustomerID { get; set; }
        [Required]
        public Guid ProductID { get; set; }
    }

}