using System;

using System.Linq;

using System.Collections.Generic;

using AutoMapper;

using Newtonsoft.Json;

using Microsoft.EntityFrameworkCore;

​

public class Program

{

    public static void Main()

    {

        MapperConfiguration _config = new MapperConfiguration(ctx => 

        {

            ctx.CreateMap<Product, ProductDto>()

                .ForMember(

                    dest => dest.Price, 

                    opt => opt.MapFrom((src, dest, member, context) => src.Price - src.Category.CategoryDiscount));

            ctx.CreateMap<Category, GetCategoryProductsDto>();

        });

        IMapper _mapper = _config.CreateMapper();

        var options = new DbContextOptionsBuilder<EntityContext>()

                .UseInMemoryDatabase(databaseName: "Add_writes_to_database")

                .Options;

        using var context = new EntityContext(options);

        List<Category> categories = new List<Category>

        {

            new Category { Id = 1, CategoryDiscount = 25 }

        };

        context.Categories.AddRange(categories);

        context.SaveChanges();

        List<Product> products = new List<Product>

        {

            new Product { Id = 1, CategoryId = 1, Price = 500 },

            new Product { Id = 2, CategoryId = 1, Price = 1000 }

        };

        context.Products.AddRange(products);

        context.SaveChanges();

        Category category = context.Categories

            .Include(x => x.Products)

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

        GetCategoryProductsDto dest = _mapper.Map<GetCategoryProductsDto>(category);

        Console.WriteLine(JsonConvert.SerializeObject(dest, Formatting.Indented));

    }

}

​

public class EntityContext : DbContext

{

    public EntityContext(DbContextOptions<EntityContext> options) : base(options)

    {

​

    }

​

    public DbSet<Category> Categories { get; set; }

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

}

​

public class Category

{

    public Category()

    {

        Products = new HashSet<Product>();

    }

​

    public int Id { get; set; }

​

    public int CategoryDiscount { get; set; }

​

    public virtual ICollection<Product> Products { get; set; }

}

​

public class Product

{

    public int Id { get; set; }

    public int CategoryId { get; set; }

​

    public decimal Price { get; set; }

​

    public virtual Category Category { get; set; } = null!;

}

​

public class GetCategoryProductsDto

{

    public int Id { get; set; }

​

    public string CategoryName { get; set; } = string.Empty;

    public int CategoryDiscount { get; set; }

​

    public List<ProductDto> Products { get; set; }

}

​

public class ProductDto

{

    public int Id { get; set; }

    public int CategoryId { get; set; }

    public string ProductName { get; set; }

    public int Qty { get; set; }

    public decimal Price { get; set; }

}