using Microsoft.EntityFrameworkCore;

using System.Linq;

using System;

using System.ComponentModel.DataAnnotations;

​

namespace EFTest

{

    // entity classes

    public class Product

    {

        public int ProductId { get; set; }

        public string Name { get; set; }

        public decimal Price { get; set; }

    }

    public class Customer

    {

        public int CustomerId { get; set; }     

        [Required]      

        public string FirstName { get; set; }

        [Required]

        public string LastName { get; set; }

    }

    public class AppDbContext  : DbContext

    {

        public AppDbContext (){ }

​

        public AppDbContext (DbContextOptions<AppDbContext > options)

            : base(options){ }

​

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

        public DbSet<Customer> Customers { get; set; }

    }   

​

    class Program

    {

        static void Main(string[] args)

        {

           var options = new DbContextOptionsBuilder<AppDbContext>()

                .UseInMemoryDatabase(Guid.NewGuid().ToString())

                .Options;           

            using var dbContext = new AppDbContext(options);

            PrepareSampleProducts(dbContext);

            //-------------------------------------------------------------------------------------------------------------------------------

            // (1) Add two new customers to the database

            //-------------------------------------------------------------------------------------------------------------------------------

​

            //-------------------------------------------------------------------------------------------------------------------------------

            // (2) Update the price of the laptop from the current 1000 to 1300

            //-------------------------------------------------------------------------------------------------------------------------------

            //-------------------------------------------------------------------------------------------------------------------------------

            // (3)  Calculation of the total price for all products in the database

            //-------------------------------------------------------------------------------------------------------------------------------

            //-------------------------------------------------------------------------------------------------------------------------------

            // (4) Can you point out the advantages and disadvantages of the following two calls No. 1 and No. 2 and explain the difference?

            //-------------------------------------------------------------------------------------------------------------------------------

            // #1

            var productQuery01 = dbContext.Products

                .AsNoTracking()

                .Single(x => x.ProductId == 1);

            // #2

            var productQuery02 = dbContext.Products

                .Single(x => x.ProductId == 2); 

            //-------------------------------------------------------------------------------------------------------------------------------

            // (5) Can you explain why query #1 more performant than #2 even though the results are the same?

            //-------------------------------------------------------------------------------------------------------------------------------

            // #1

            var result1 = dbContext.Products.Where(x => x.Price > 100).ToList();

            // #2

            var products = dbContext.Products.ToList();

            var result2 = products.Where(x => x.Price > 100);

            DumpDatabaseTables(dbContext);          

        }

        private static void DumpDatabaseTables(AppDbContext dbContext)

        {

            FiddleHelper.WriteTable("Customers", dbContext.Customers);          

            FiddleHelper.WriteTable("Products", dbContext.Products);    

        }

        static void PrepareSampleProducts(AppDbContext dbContext)

        {           

            var lpatop = new Product { Name = "Laptop", Price = 1000 };dbContext.Products.Add(lpatop);

            var tv = new Product { Name = "TV", Price = 500 };dbContext.Products.Add(tv);

            var shirt = new Product { Name = "Shirt", Price = 20 };dbContext.Products.Add(shirt);

            dbContext.SaveChanges();

        }

    }

​

}